The 125w is just the maximum the speakers can handle (like the red line for a car) and not how much power that you need. The JBLs are 8ohm speakers so you really don't need anything special to drive them.
The problem is that we don't know the connections available on your computer. Assuming that it has an optical-out connection from the on-board sound card you would use that to connect to the receiver via a
toslink cable. Nearly all audio/video receivers (AVRs) have an optical input.
You'll need a couple of
subwoofer cables long enough to reach the subs. And since budget is probably limited you'll probably want a SPL meter (~$40 @ Radio Shack) to help balance the output from the subs. High-end receivers can do that for you but I'm assuming that you don't have a $1200 budget. If you don't mind factory refurbished then a Denon
AVR-2112 or
AVR-2312 from Accessories For Less are bargains that you aren't likely to outgrown anytime soon.
