I am very excited, because probably the most important number to pull in order to arrest or reverse arterial plaque is something called LDL-P, or the "LDL Particle Count." "Regular" LDL - the kind you are used to on your annual physical - is actually LDL-C. It is an important number, but is not the kind most tightly correlated to heart disease. And the reason is that it is really the number of LDL particles (LDL-P) that most determines how much of the LDL will be driven into the lining of your arteries. LDL-C is probably important primarily, because it is so correlated to LDL-P.
However, there is a problem with LDL-P: most doctors will not pull it for you and it is currently pretty expensive to pull yourself. Many physicians do not yet understand the importance of LDL-P and are not interested in "unnecessary testing", i.e. testing you before develop angina or drop dead from a heart attack! In my opinion, LDL-P should a part of every man's yearly physical. Unfortunately, if a man tries to pull LDL-P himself, the cheapest cost from what I have seen is in the $125-$150 range.
The good news is that there is another marker out there that one can use in place of LDL-P: apolipoprotein B (apoB). From all I have read - of course do your own research - this number essentially parallels LDL-P and it is MUCH cheaper. For example, you can get this at Health Tests Direct for $35, assuming you don't live in one of the states that doesn't allow testing. See my page on Testosterone Labs for more information.
Like LDL-P, apoB has been closely tied to IMT scores, i.e. the development of arterial plaque, in multiple studies. One paper noted that apoB is also tied to cardiac events, i.e. angina, heart attacks, etc.:
"Although LDL cholesterol (LDL-C) is associated with an increased risk of coronary heart disease, other lipoproteins and their constituents, apolipoproteins, may play an important role in atherosclerosis. Elevated levels of apolipoprotein (apo) B, a constituent of atherogenic lipoproteins, and reduced levels of apo A-I, a component of anti-atherogenic HDL, are associated with increased cardiac events." 
So why should a man be interested in managing his arterial plaque? Well, besides the fact that he could drop dead from a heart attack, plaque is also tied to nitric oxide production and erectile function. Yes, as plaque builds up in those penile arteries, things will softer and slower in the bedroom.
The burning question in my mind is always what I can do to keep arterial plaque from increasing and possibly even reverse it. To do this, let's look at some of the targets that may achieve just that for us:
1. Dr. Davis' Target. The best book on the market when it comes to cardiovascular markers for atheroslcerosis is Dr. Davis' book and you can read my praise and appraisal of it here: A Review of Track Your Plaque. In order to reverse plaque, Dr. Davis' recommended apoB of 60 or less.  This is a very aggressive requirement and Dr. Davis uses high dose niacin to achieve his goals generally. And, in addition, keep in mind that he is dealing generally with patients that have existing heart disease and definitely need to reverse plaque.
That said, it's better safe than sorry and so you may want to shoot for this target. However, keep in mind that Dr. Davis recommends LDL-C levels below 60 mg/dl and I have seen other reliable sources recommend between 70 and 80 for plaque reversal.
2. Go For The Top Five Percent. According to some Lipid Center data, if you want to be in the top five percent of apoB scores, you would need to have a level of 62 mg/dl or below.  This is probably a reasonably solid number as about 5 percent of Americans have no atherosclerosis and notice that it corresponds fairly closely to Dr. Davis' 60 threshold. If you want to be in the top 2 percent, you would have to be well below that at 54 mg/dl according to the same report.
3. ~100 mg/dl in Higher Cholesterol Patients?. There is an interesting study out there that put patients with higher cholesterol on either a statin or high dose niacin. You may recongize these as the two agents that the Plaque Regressers Dr. Gould and Dr. Davis use on most of their patients. A statin works primarily by lowering the over LDL numbers and niacin by moving the LDL away from a "pattern B," i.e. less small particle LDL and triglcyerides. What is interesting is that both strategies decreased narrowing of the arteries in a multiyear study even though their apoB levels were not really that low. ApoB levels were 103 and 111 mg/dl in the lovastatin and niacin groups, respectively and yet they still experienced plaque regression.  Is it easier for higher cholesterol patients to regress plaque? I don't know, but I would aim for lower apoB numbers to play it safe.
4 Verify with an LDL-P Blood Draw. You can also pull your LDL-P (LDL Particle Count) and verify using that as mentioned above. To get an idea for levels to reverse plaque using this marker, see my page LDL-P and Plaque Reversal and LDL-P Particle Count Levels.
DIET ALONE? Can you achieve a satisfactory apoB score with just diet alone. I can tell you that I am currently on a low glycemic, low fat diet and exercizing and hour per day. Doing just this I have been able to get my apoB down to 68 mg/dl without niacin or a statin. This is a good start in my opinion, but I'd like to drop it below 65 if at all possible.
2) Track Your Plaque, by Dr. William Davis, iUniverse, p. 93.
3) N Engl J Med, 1990; 323:1289-1298, "Regression of Coronary Artery Disease as a Result of Intensive Lipid-Lowering Therapy in Men with High Levels of Apolipoprotein B"
4) J Intern Med, 2004 Feb, 255(2):188-205, "Apolipoprotein B and apolipoprotein A-I: risk indicators of coronary heart disease and targets for lipid-modifying therapy."