I just got my new Morphenspectra footwell sub-woofer enclosure and now have to decide on a speaker for it.

I'm thinking of going Rockford Fosgate. I have the adapter ring so an 8" will work.

Anybody have a recommendation?

Rockford Fosgate P2D48 8" Sub.

Dont waste your money on RF. Go with JL Audio and a dual voice coil if at all possible.... You'll be pleased. make sure the sub you choose can work with the small amount of box it's getting.

I have had a set of RF's for 15 years, they sound good...And lasted 15 years so far.

Like Purple says, check to make sure it can work optimally with the volume you have. Also check the available depth you have. That RF looks very deep.
I've got a Polk 10" in mine. Great with the top off, but I usually have to turn the bass way down with the top on (just too much!).

I've got almost .50 of cubic feet to work with. The recommended space for this speaker is .20 - .30.

Depth is fine with the spacer that came with the box.

I'll look at the JL Audio stuff as well.

if you have more box than recommended for the sub (.50 really isnt big at all, at least compared to the 2.0's i had with my dual 12''s back in my protege days) then it will sound wrong, really boomy and uncontrolled. You need to closely match the sub to the box. is this a sealed or bandpass box? I'm going to assume sealed. You need 2-3 times the power of your speakers for a sealed box to hit correctly. otherwise it just sounds weak. amps are important, since you're shopping for RF's, i'm going to assume you're also shopping for sony xlpod amps...dont do this.

Go with JL or memphis audio. I like memphis because they rate conservatively and dont bullshit you with peak 9000watts like sony xplod does. look for RMS and match that to the sub's RMS if you can. the money is in the amp-sub combo. get this right, and you've got something awesome. also, never skimp on wires...

The one pictured looks too deep.

It's actually only 4.65 inches deep surface mounted.

The entire system in my Titan is R-F. 300 watt amp and sub under the front seat. No idea how large the sub is, but it's certainly the best car stereo I have. Well the Acura Bose unit is probably better, but it needs the bass from the truck!

when i do mine, im gonna to an alpine type r sub.

i know 2 people with em, and they sound great, with great clarity even with heavy bass