should i get a new amp?

I just recently installed a pair of boston acoustics pro 60's in my front doors and have them powered off an old punch amp. It is rated at 90x2 at 4 ohms (pro60's are rated at 3 ohms, 125w rms) so I figure I have sufficent power to them. The gain knobs require a small screwdriver and they have been destroyed by the previous owner so left and right gain are permanently set all the way up. First question is,since the amp works fine should I upgrade it to get the best sound from speakers? Is it worth the $300 or so for a good amp or will difference not be that noticeable? If so I have made myself dizzy reading posts about amps to see what to look for. Should I go with the JL audio 300/2 over say an alpine pdx or boston acoustics amp because the s/n ratio is 108.5 db over the 105 from boston to the 94 or so from alpine? Does the .03 THD from the JL make it superior to the .1 to the others? Everything is being run from a kenwood exceleon x889 headunit and as soon as I get my box finished the sub will be a boston 10"  G5 being powered by a kenwood excelon x20 (505wrms @4ohms).

JL makes very good products. I dont know much about their amps though but rather more about their subs. I honestly dont look at S/N ratio or their THD. But I will say that JL is a pretty reliable brand. You need to watch out for some companies. They like to "lie" about what their products can do. I have already seen amps that are listed at 2000 watts yet only have 2 25 amp fuses.

That is one thing I like about the JL, it makes 150wx2 no matter the input voltage or ohm load (within normal specs of course). My bostons are rated at 125w rms so I think this amp would be perfect. I can get it for $300 at woofersetc but I just want to make sure I am making the right choice.