Yamaha RX-V595a vs Denon AVR-1800 vs Onkyo TX-DS575 vs Sony STR-DE925

[Patz]

I'm planning on upgrading my old Sony Pro-Logic receiver to one that's
capable of doing DTS, and am considering the Yamaha RX-V595a, the Denon
AVR-1800, the Onkyo TX-DS575 and the Sony STR-DE925.
I've read favorable reviews of all of them, but am having some trouble
trynig to decide which is better. I'm kinda leaning towards the Yamaha, but
am open to suggestions.
This is my tentative home theater system:
*Front Speakers: Infinity Delta 40
*Center Channel: Infinity Delta Center
*Surrounds: Infinity QPS-1
*Sub: None
*DVD/CD Player: Toshiba SD4109x 6-Disc Carousel DVD player
*TV: Toshiba/Sony 27"/32" TV

Which receiver will work best with these components? Considering that I do
not really crank up the volume most of the time, how much power from the
receiver do I really need to drive this system in a 18'x11' room, with my TV
about 7' from where I sit? BTW, are my speakers decent? Any other
suggestions?
Thanx guys!

Kind Regards,
Patrick