blu-ray vs DVD audio over stereo

[MacinMan]

Hey guys,
I have a couple questions here concerning an apartment setup.
1. for the sake of space and not disturbing neighbors I don't want to go all out on a whole new audio setup because i'd never enjoy it in full due to having to keep the volume down most of the time.

My current living room setup

Panasonic 42" Plasma
Sony BDP-S570 blu-ray player.
a 7 year old Panasonic home theater in a box.
The panasonic HTIB only supports true 5.1 surround with the built in 5 disc changer only. However, it supports red and white stereo inputs from external devices. In addition to this it will allow dolby pro logic and other virtual surround modes to such inputs. Currently I'm just getting BD audio via the tv speakers with HDMI. Will i get decent sound by connecting the stereo out from the bd player to the htib in? and set pro logic on? or another surround mode? the sony downmixes bd audio to surround by default. I figured 2.1 would be better then tv speakers anyway left right and the sub. anyway the tv has pretty good sound for the speaker size.

Thanks for the feedback!

Clint