Tight fit for HDMI, short speaker cable

As long as your HDMI cable runs aren't super long (and the definition of that will vary depending on the type of cable, quality of its construction, the source and destination equipment, etc etc) then an L adapter should not noticeably degrade the signal.

The speaker wire should be fine as long as the splice is properly-made (meaning the wires are not loose and could pull apart at any minute). Best option is to solder it. You could also use butt splices.

HDMI is digital, no loss. As far as the speakers, make sure to use the same gauge wire. Wire nuts, butt-splice, solder, won't make a difference.

There is no particular reason to use the same gauge wire.

Also, there are short HDMI whips/pigtails which are great for situations like this where you have a very large inflexible HDMI cable:

http://www.monoprice.com/products/pr...seq=1&format=2

You can find similar products from comparable vendors as well, such as blue jeans cable, etc.

I had the same problem and was also worried about cooling. Plus, as I am tweaking my system, I got tired of dealing with the small'ish holes in back, having to pull the AVR out the front to connect things, then fiddle with the wires to thread the AVR back in place. My solution was to saw open the back so the back of the AVR was essentially open. I was careful to leave plenty of material on the back around and above the AVR (mine is on the bottom) so structural integrity was not significantly compromised (the back is essential to stability on a lot of entertainment units). I can easily see/reach all the connections in back, the AVR runs cooler, and the stand seems as stable as ever.

FWIWFM - Don