Need help with Subwoofer and amp?

Kicker makes a variety of 10" subs ranging from 150w rms to around 1000w rms.

Since it was suggested you get a 300w amp my guess is you have the basic Comp 10's. Those are 150w rms each, and most likely 4 ohms.

Since those are lower power subs and you have the 2nd one on hand I would go ahead and use it.

Legacy is one of the lowest quality amps available and advertises power ratings it is no where near capable of meeting. Dual is better, but only slightly.

You should be looking for a mono amp that is around 300w rms at 2 ohms. Having a pair of 4 ohm subs allows you to wire them parallel for 2 ohms: http://m.seimg.net/product/img/subwoofer_wiring/2_subs_SVC_4_ohm_mono.jpg

Some possibilities:
http://www.sonicelectronix.com/item_33006_MB-Quart-FX1.400.html
http://www.sonicelectronix.com/item_22644_Clarion-XR2110.html
http://www.sonicelectronix.com/item_21786_JBL-GTA3011.html

The subs will need a box as well:
http://www.sonicelectronix.com/item_34506_House-Brand-10DSPF.html

Also an amp kit:
http://www.sonicelectronix.com/item_20526_Absolute-KIT-8-KIT8.html

get 500 watt amp if you want to power both of them any kicker amp will do beast kicker.com