the RS6 is a real nice car...very powerful, quattro and i think it looks good but...
if money is not a big deal to you, then get the RS6, cause it will be VERY expensive to own for a few years.
it seems though that the cost of selling and buying is a big deal to you.
i'd suggest a 2007 335i...,depending on mileage and options/packages you could probably get a nice one for high 20's if you look hard enough.
2007 e90 335i SG/Beige/Dark Burl-Premium : Sport-6MT : CA : iPod Adapter : 18" OZ Superleggera III w/ ContiSportContact 235F, 255R : 18" Rial w/ Blizzaks 225F+R : Hamann-style front splitter : 35% Tint : Aluminum pedals...Sunglass holder, Blacklines soon.