4 channel amplifier: MB QUART vs ALPINE... opinions?

[KingTen91]

(I felt the original post was a little lengthy so I shortened it to what I felt was more of the essentials)
Interested in your opinions and any helpful feedback or experience. Thanks in advance.
I just installed a set of Polk dxi 6501 components in my front doors. The old speakers (original speakers btw) were blown (passenger spk the woofer was completely separated from the cone, driver spk was seized up, not budging at all) I don't really feel comfortable running these solely off of my kenwood head unit (which came with the car) as I'm imagining I'm prob only receiving around 20 watts to supply the speakers. So I've been looking at getting a 4 channel amp.

Amps I'm considering:

Alpine mrv-f300....50 watts per channel..$200
Alpine mrx-f350....55 watts per channel..$180
^^(mrx marked down from original $300)

MB Quart OA800..100 watts per channel..$120
MB Quart OA600..75 watts per channel..$100

Some things I'm considering:

--The alpine mrx 55 watt is from a higher end line from alpine, but apparently it's on sale because it's a discontinued line,.. is that because something bad, like too many complaints? Or something good, like maybe it was too expensive to produce?
-- I've heard MB-Q is crap now that they're not German, that is except for their 4 channel amps, which a few people seemed to be in agreement that they still made quality.
--I noticed crutchfield doesn't carry MB-Quart.. which kind of had me worried, but I called and even though they don't carry them the representative claimed that when they did carry them they were amazing, and that just because they don't anymore shouldn't insinuate that changed. So maybe it's a logistic thing?

In your opinions, what do you think. Is ALPINE worth the difference? Or will MB-Q be good enough for just a 4chan?
I do appreciate any help and info given, thanks

[KingGeorgeXIII]

I'm having trouble finding any real specs on those amps. If I were making the decision myself, I would buy the lowest THD rated class AB amp with 50W per channel that didn't go over my budget. Remember you want the rated distortion at rated power, not at 1 watt. (or at least make sure you're comparing like-to-like)

I've built modest, good sounding systems in two cars, and used Pioneer amps both times. a 2-channel and a 4-channel. The 2 channel sounded fantastic and ran for years with no issues, the 4-channel sounded good, but never quite right and burned up after less than a year. They were from the same "family", with the 4 channel just having twice as much circuitry in it, so I suspect that it was just defective. Swapped my old 2-channel in and it sounded better running just the front components than the full set of 4 ever did. If you do some research, you'll find that ditching the rear speakers and just running 2 channels + (optional) sub is the direction frequently taken for the best sound quality.

edit: If you go with just 2 channels and you want it to be REALLY loud without distorting, go with 75W/channel (easier, and probably cheaper), or else make sure your speakers have a higher sensitivity rating than the speakers I used, Pioneer D-series 6 3/4" components. (sometimes difficult information to find, and high sensitivity ratings are usually found on very expensive speakers) They were loud, probably loud enough to cause hearing damage, but really pushing the system would still make it distort. +3dB sensitivity means the speakers are TWICE as loud with the same power.