Re: 2 ohms on 4 ohm amp..
Depends solely on the amp, and how well it was built.
*Alpine CDM-9803 Head Unit <-- New Alpine HU, forgot model #.
*Front Coaxials - Pioneer 6.5" 3-ways. No rears.
*Speaker Amp - Hifonics TXI4408.
*Infinity Perfect 10.1 Subwoofer.
*IB Mounted to dear deck, sealed from cabin.
*6 Gauge wiring, to amp. All 14 gauge wiring for speakers and 12 gauge to sub. Cheap Home Depot RCA's.
HU - $80. Sub - $50. Coaxial's - $20. Wiring - $20. Amplifier - $90.
For under $300, a complete system that sounds rather good for what it is.