Start with the volume low and listen carefully for distortion as you raise the volume.
My fear would be clipping from a weak (or not capable of handling the impedance of your speakers) AVR.
It might be wise to simply test one speaker at a time (still listening for distortion and backing away if your hear bad sounds) since the AVR should be more cable with only a single speaker.
Some of these HTiB can be pretty weird with the amp section designed for 16 ohm speakers... or more designed for 4 ohm speakers like a car stereo. When the manufacturer knows exactly which speakers will be used (as in an HTiB), they can get away with cutting cost by designing the amp specifically for those speakers.
You might also check Craigslist for receivers, there are some good deals to be had there on AVR's that don't have HDMI connections (assuming your TV and DVD player don't require HDMI). I've seen some good 5 channel units going for $40-75, and that might be worth holding you over if you don't expect to (or would rather not have to) get funds for the 3400 too soon.
The good thing about a $50 receiver is, as long as it works, you should pretty much be able to sell it for about the same - it was already well used and your having it for 6 months won't depreciate it very much.
If you want, post a link to your local Craigslist and we can see what looks good.
