Marantz 5500 vs Denon 2105

Upgrading a generic sony surround sound setup. I am looking first at the recieverupgrade.
Set up now is Panasonic 47" HDTV projection.
Sony DTS 5.1 reciever and 5 speakers/sub.
Panasonic 5 disc DVD
Comcast Cable HDTV box
I noticed a feature that I really want which is the upconversion to component plugs. Which if I understand correctly means that eliminates my need to switch my HDTV panasonic between video 1, 2 etc.
Here are my possible choices from what I've reserached.
A/R receivers with component up conversion

Marantz SR 5500 $499
Yamaha RX-V750 $397
Denon AVR-2105 $429

As far as speakers, HSU research and paradigm speakers seem to be very highly regarded. But I have not put much time into it yet, concentrating on recievers first.

Oh room size is no bigger then 20x10

Any suggestions pro or con for any of these recievers and or speaker/reciever combinations?
Thanks in advance.