The MDX sells fairly well, because it competes mostly with other SUVS of similar size, utility, price, and power. People cross-shopping it will look at the RX330, a 3.0L X5, ML320, etc... Fortunately the market for those SUVs is fairly large and Acura has fielded a competitive car that has class-leading power (or at least near the top) that also has good value and quality. However, I doubt anyone looks at the MDX as a serious competitor to V8 editions of those same SUVs, or other V8-only luxury SUVs. The new RL "would" (in theory) need a V8 because all of the cars it will be cross-shopped against have V8s and more power. Not having that is a big sore thumb and a minus for a lot of prospective buyers. Unless Honda has something else in sotre, say like IMA, to help offset that, then I see the use of a V6 as a big negative. It may not make much difference in terms of performance, but it will in perception.