When deciding which amp will push this or that.....check the fuses
for every 10A worth of fuses, thats 100watts of power.
so if your legacy amp says 1000watts but only has a 30A fuse in it, guess what?
But even if you have say an amp with 5 30A fuses you still are not getting the full
1500watts if you havent upgraded the big 3 and your alternater/battery.
and BTW, there is an credible argument going on that you cant even hear the
difference in amps, as long as the total power ( and total fuses) are the same.
all else being equal just look for features you like, such as remote bass, shiny chrome finish , number of channels, etc.
PS. on unfused amps (RF), look for some sort of certificate thats states the total max power or check what the manufactor recommends for the in-line fuse.