2002 Camry JBL Amp Bypass Questions

[tsunami644]

I have the 6-Disc JBL system on my 2002 Camry and it suddenly went out. Whenever I press the power button, nothing happens. I checked the fuse box and the fuse is intact so I just decided to replace the head unit. I have gone to Car Toys, Tweeter, Best Buy and Circuit City, and everyone has told me that I have to bypass the amp because JBL adds a proprietary connection from the head unit to the amplifier.

I was just about to buy a Sony CDX-GT610UI from Circuit City (installation would cost $100 including bypassing the amp) when the guy told me that I would also have to replace all four of my speakers. His reasoning was that because the Sony had a higher "Ohm rating" it would blow my current speakers and even if it didn't blow them, I wouldn't get any bass from them. Is what this guy was saying true or not? None of the people at any of the other stores told me that I had to buy new speakers also. I was very happy with the JBL system's sound and I would have kept using it if it didn't stop working all of a sudden. Would this system sound much worse if I didn't replace the speakers?

Another question I have is, how complicated it is it to bypass the amp on my own? Will I have to wire all of my speakers? Or is it just a matter of swapping some wires behind the head unit. I don't mind paying for installation, but if they do a crappy job just so that I have to buy some speakers from them I'd rather do it on my own. I read cam2Xrunner's tutorial and I was curious as to whether it would apply to my car also.

My main questions are just whether sound quality will suffer when I bypass the amp and whether or not I can use my current speakers.

Thanks for your time.