yeah, you'd be hard pressed to keep under 300 bucks. Here's what I just bought for my truck:

Combo: Rockford Fosgate PRIME R500-1 Amplifier + 4 Gauge Amp Kit

Rockford Fosgate P3L-S12 (p3ls12) - Non-Amplified, Loaded Subwoofer Enclosure Systems - Sonic Electronix

Scosche LOC-80 (loc80) - Line-Out Converters - Sonic Electronix

That's 400 bucks for something not too fancy.