I've noticed power sub having many variations of amp power and wanted to know if there are things to look for when choosing a sub. Does it matter as far as driver size? Does more power = more db@(x)hz? I've seen sub's with 1000 watt amps and some with 15" drivers with only 100 watts. Why is this. ALso, for SVS unpowered or nay other unpowered sub, many say "any" amp would do, if so then why buy the optional amps many companies offer that are more expensive and more power if you don't "need" it? EX: old Sony receiver driving a SVS 25-31 or Marantz MA 700...would there be a difference in sound quality? Hope this makes sense..thanks guys.