How does this setup sound ?

The nice thing about the SR5005 is that it has bass management (Audyssey MultEQ XT). While a very good quality 2-channel receiver, the HK 3490 offers no bass management and the subwoofer connections are full range. Since you are planning on 5.1 later the SR5005 would seem to make the most sense. Great choice on the speakers.

It sounds like you are off to a good start. IMO, its important at some point to decide what your emphasis is going to be. Are you going to focus on 2.1 or not? If you are looking for 'good' surround sound for movies but arent to picky on the absolute quality of stereo sound then where you are going is the path you should be on. If you have a limited budget, but want audiophile level stereo sound, it might be better to forget about the 'receiver' approach. Just my opinion. It's hard enough to tune a 2.1 let alone surround sound. There is plenty of good kit out there but you have to look at 'separates' to really get the best bang for the stereo buck.