First off, the E4300 is discoed.
If you want to know the big difference between JLs two series of amps, the slash series and what is now the A series (formerly E), then check this out
http://mobile.jlaudio.com/products_a...php?page_id=29
This is a tuff call for me. Normally I'm quick to jump on the Slash JL because I think with their advance circuitry, they are among the best amps available period! There is more to the JL Slash series than many users can understand. Its all about a different approach to circuitry and connection. For instance, due to an adaptive power supply, the JL 300/4 actually delivers near DOUBLE the rated power when connected to 4ohm speakers. The power is among the cleanest you'll find.
The PDX 4.150 is AWESOME! However, not exactly my first choice. I personally like a strong presence of Midbass in my car. The absolute only thing the 4.150 appears to lack is a bit of a strong lower-mid presence. A speaker w/ good sensitivity can help make up for that a little, but Still, I don't think it will rival the JL in that dept. As IRON points out, the Alpine is 150x4 @ 2 or 4ohms. The adaptive Power supply in the JL allow for all slash series amps to maintain thier power rating @ any impedence they are stable at. The build quality of the slash series gives you your money's worth and then some. Overall, I am torn between the two amps, I'd rather an A/B class on my interior front stage most days, due to typically better freq response, althought I think the 4.150 has better-than-average to begin with. I would have to say that still the JL Audio and their masterful crafting of the slash series is your best bet. Throw out bench tests and take it on a music-and-speaker level, the JL slash will challenge almost any amp out there. I have never heard a more musical, more accurate amp in my life. My 300/4 made all three sets of speakers I connected to it come to life in ways I haven't hear. Quart Q series, CDT CL61s and Focal Utopia were all at their most brilliant and the realism and imaging of the sound was jaw dropping. All had PLENTY of power and with a nice 4v signal from the Alpine up front I was able to provide ample power to any speaker set and still keep my gains low low.