I didn't care for my 18" Fi Q, but thats besides the point.
I wouldn't pay over 300 for the pair of G5s, personally as thats what I've seen them go for a few times on
eBay so I know what I can get them for.
I listen to mainly rap music myself and in all honesty, any sub that sounds nice on other genres of music will also do well on rap. Just be sure to have the right box tuning.
The Dayton sub is a diamond in the rough. I think the price of it misleads people a lot. You need to spend over double the price to beat it SQ-wise, in my experience, and even then, it holds its own. The sub has a very flat frequency response with legit low end extension and transparency that most subs simply cannot offer, in and out of its price range. It shines in tiny boxes so you don't have to take up as much space as your typical sub, but it will in fact outdo most of them.
Here's one quick vid of mine from when I ran them in my tC (2 Dayton HO 10s in 0.7cubes each tuned to 29hz on about 400w per sub) :
http://www.youtube.com/watch?v=HGMbUpZCbDo
the low note in that song is like 24hz or so, exactly when that alarm goes off.
They aren't crazy loud, so don't expect to compete in SPL competitions with them. But, they sound amazing and got plenty loud for me.