What sub? 120 rms at 4 ohm, to add low end to moms car

[4x4runner 10+ year member]

I am putting a stereo in my moms car for her. she wants an upgrade over the factory bose in here 01 audi s4. Waiting for everything now in transit. its a alpine cda-105 , alpine mrp-f320 amp, mb quart discus 5.25 component and 6.5" coax. The amp is 40x4 and 120x1 at 4 ohm 5 channel. I am looking for a sub to possible add on the 5th channel to add some low end. Not looking for spl at all and something to go well in a small sealed or maybe ported box. under $50 shipped preferably. I was thinking alpine type s 10, hifonics hfi12 ($26 shipped lol) , or mb quart discus 12. would probably prefer a 10 but alot of the cheaper subs dont come in a 10" size. But with only 120 rms at 4 ohm im not sure these subs would be best. any recommendations?

How about this sub

http://www.sonicelectronix.com/item_20057_Pioneer-TS-W253R.html

I like this but i can't find any info on this amp if the sub channel is stable at 2 ohms, its an old school amp. But for her im sure the 120 rms is sufficient., just cant find this sub is dual 2 ohm coils

http://www.sonicelectronix.com/item_27301_RE-Audio-REX10D4.html

Click to read more...

 

[mclerico83 5,000+ posts]

NEW Phoenix Gold RSD10 10" 4-ohm subwoofer 500 Watts - eBay (item 160448099888 end time Mar-19-11 14:31:38 PDT)

spend the extra 20 and get this look at the reviews. its been compared to the idmax in sound quality

Phoenix Gold Phorum • View topic - RSD 10" Mini-Review

Phoenix Gold RSD12 Car Audio Test Report - Review Reviews - Car Audio and Electronics

New Powerbass S-104 Single Voice Coil 4 OHM 10" SUB - eBay (item 390292033496 end time Mar-05-11 19:33:53 PST)

id do the pb over the hifonics

NEW T3 T20010S AUDIO 10" CAR 4-OHM 400 WATTS SUB WOOFER - eBay (item 290532226956 end time Mar-10-11 08:00:17 PST)

JBL GT5-10 10" Single 4 ohm GT Series Subwoofer New! - eBay (item 110653683710 end time Mar-03-11 13:51:47 PST)

this is an amazing sub also

 

[Rich B 5,000+ posts]

I would just buy a loaded box with a decent brand sub, the lower priced ones will probably be just right power handling wise.

 

[dragonrage 10+ year member]

Peerless SLS