Ok, so I basically was given a 1000 W 5.1 HTIB a year ago. The speakers are adquate for my use and room size.

I connect to the receiver:
Xbox 360
Scientific Atlanta 8300HD
Hitachi 55hds69 Plasma

Now I have the issue that I am out of optical inputs which generally happens with HTIB's. So here are my options:

1. Optical to Coaxial converter, these get pretty good reviews on monoprice
http://www.monoprice.com/products/product.asp?c_id=104&cp_id=10423&cs_id=1042302&p_id=2948&style=&seq=1&format=4#feedback Grand Cost: $12

2. Optical Switch, this is probably out since it's manual. Grand Cost: $30

3. Buy a new receiver, here is where I have questions. I would buy one with HDMI connectivity, but I am wondering how my current speakers will work with a different receiver. Cost $150 after some coupons I have

I am looking at a Sony STR-DG510, like I said I am content with my sound now, but the HTIB receiver is limited in sound options (only bass/treble control & Dolby 5.1)

The other issue is that the speakers are all 4 ohm impedence, therefore, how would this receiver work with the different impedence and lower power levels.

Thanks for any help