Head units are not my forte, I'm old school CD playback, DEH-80/880/99PRS old school. There are a number of folks in here with a lot more HU experience than me. I guess I'll get up to speed when my last 80-PRS dies, but that will be a while, still have another instorage and 99s are still out there!
As for 4 channel amplifiers on a budget (price being a serious consideration here), lots to choose from. I would recommend sticking to units that can utilize high level inputs, then you can wir it straight to the HU of choices.
Class A/B
$95 on
amazon, here is the model on
ebay
Class A/B 4-Channel Amplifier, 1040 Watts Max Power, RMS 130 Watts x 4 Channels@2 Ohm; RMS 95 Watts x 4@4Ohm; RMS Power (Bridged): 260 Watts x 2@4Ohm. Highly efficient heatsinks keep the amplifier cool with a sophisticated new look.
Full range class D
The recoil site is down this morning but check out their $85 4 channel full range Class D, I think it is the REA600.4?, it's a decent power unit and the price is right.
$140
CT Sounds engineered the CT-80.4AB Full-Range Class AB Multichannel Car Amplifier for anyone in need of a powerhouse amplifier that fits just about anywhere in your vehicle and won’t destroy your wallet.
$114
DS18’s GEN-X Series is back to boost all systems to top-of-the-line performance! DS18 PW-OFC4GA-50CMGR 4-GA Ground Power Cable 50 FT Flex 100% OFC Camo Green. DS18 PW-OFC4GA-50YL 4-GA Ultra Flex 100% OFC Ground Power Cable 50 Feet Yellow.
$125
@ 14.4 VDC - 2 OHMS: 800W RMS (4 x 200W RMS). @ 14.4 VDC - 4 OHMS: 544W RMS (4 x 136W RMS). 2 Bridged channels 4 OHMS: 400W RMS (2 x 400W RMS). This feature makes it ideal for this type of application, eliminating the need for adapters.
$140
The amp's compact size (330mm x 52mm x 240mm) makes it easy to install in a variety of spaces. Total Max Power: 600W. EQ (Equalizer): Bass EQ Fixed Frequency 45 Hz, Q=0.5, Variable Gain 0dB to +12dB (3/4 Ch only).
$132
Pioneer GM-D8704 600W Class FD 4-Channel GM Digital Series Amplifier w/ Wired Bass Boost Remote. GM Digital Series 4-Channel Class FD Car Amplifier w/ Wired Bass Boost Remote. 4 gauge power and ground wiring is required for installation.
$67 (cheap power, not a fan of the connector type or the crossovers, might not matter in this scenario)
So why wait?. Perfect for use in vehicles, this amplifier is optimized for 2 ohm impedance and provides exceptional performance.