now that there's a link to the condo in question on the first post... yeah, that's a glorified, overpriced NIC condo. it looks pretty, but the design is impractical. as I said, you can make something BETTER than that for half the price or less.
as Jenny said, I'd go with 4Lx2W for an elop. carpet's very iffy - there are better/safer flooring choices. dowels will be a must to keep the levels sturdy and even (I used a few on mine, they help TONS). that condo has doors that are only one panel wide - you definitely want a door on each level that's two panels wide (so your shoulders fit into the condo, making it possible to reach the back edges to clean). ramps are space-hoggers and are totally unnecessary for levels 1 grid apart - rabbits can easily jump up 14''. you also probably want at least one level of the condo to be two grids tall so he can stretch upright fully inside it.
I also agree that each rabbit is different and each condo ends up being different - pretty much everyone who's ever built one has made adjustments/renovations at some point, which is much easier to do with a condo you've built yourself compared to that pre-made and can pretty much always be accomplished with the spare bits you've got left over from the original construction.
if you want more cage ideas, check out this thread -
http://www.rabbitsonline.net/f69/your-2012-cages-youve-made-64844/
tons of people have posted their cages in there, so there's a lot of variety.
a NIC condo really is stupidly easy to make yourself and almost everyone here with an indoor bunny has built one, so if you run into any trouble at all, you'll be able to come to us for advice/help