which I know I don't need (bigger is not always better

Even if you don't plan to play loud, a big amp can produce cleaner sound, just as SE_Sport_Driver said. What you do is turn the input gain on the amplifier down, so that you can turn the volume on the empeg up. This gives it a better signal-to-noise ratio.

When you mentioned your friend's amplifier, was that merely for comparison, or is it being offered to you as a gift? If it's a gift, definitely don't turn it down.

I'm not sure what speaker system your Jetta has. If it's four speakers, then any midrange four-channel amp should do fine. Were you going to have it professionally installed, or install it yourself, or have someone help you, or what?