I've had great experiences with the JL Audio amps you see pictured in my post above. A few tips:
Don't buy generic equipment.
You get what you pay for.
Most importantly, aim for upgradability! To start your system, think. For example, for your first amp, I suggest buying a 4 channel amplifier that is capable of running in 2 channel, 3 channel or 4 channel mode. Something with a power rating like ... 4x35w, 4x50w or 4x75w.
Thinking about this in greater detail, with this single 4-channel amplifier, you can run your mids and highs (front L/R) off of two channels, then "bridge" channels 3 and 4 to make a single (mono/bridged) channel so you can power your subwoofer (let me know if you need more explanation on what this means.). Basically, with a 4-channel amp, if it will handle 4/3/2 channels that is rated at 4x50w, you can:
Do 4 channels at 50w each: this amp can push front L/R and rear L/R, so you can run all mids and highs in your vehicle off of it - each channel will get 50w each. Doesn't seem like much wattage, but it actually is...remember, your radio uses cheap, light, small equipment that won't overheat - so in reality, 50w from an amp is in reality 10x more stable/powerful/capable than 50w from a radio.
Do 3 channels, 2 @ 50w and one at 100w or more: run front L/R mids at 50w each (or all mids and highs, if wired correctly) and bridge the other 2 channels to make one subwoofer channel.
Do 2 channels: Run both channels in bridged mode and either push two subwoofers indepenednetly or run your front L/R or rear L/R off this one amp.
So, using this configuration you start out with one amp to power your highs and mids. It will allow you to run your whole system for a while until you can afford to buy a dedicated subwoofer or a second mids/highs amplifier. Later, you can buy another amp to add to your system and move some load off of the first amp(s). It's very economical and will keep you sane with good power in the meantime.
If I were you, I would first buy a 4 channel amp - push front L/R and a single subwoofer with it. Second, buy another 2 or 4 channel amp - take the first amp, power all my mids and highs off of it, then use the new one to drive my subwoofer. Last, buy one final 1, 2 or 4 channel amp, using the previous two to push my mids and highs, then the new one to push my subwoofer.
Finally, when you have all your amps, think about upgrading speakers.
I would try to stagger your rear/front wattage in the end. So, for example, use a 4x35w amp for your rear mids/highs and a 4x50w amp for the front mids/highs.
Two last things you need to know about wiring -
1) When I say "wired correctly" above, you need to understand the two basic ways to wire up speakers: in Parallel and in Series. I would explain this to you, but it is so perfectly described with pictures at this one website that it would be stupid for me to try
Here's the link:
http://www.bcae1.com/spkrmlti.htm --- Check it out.
2) Depending on how you wire your speakers (based on #1 above), the ohm ratings on your speakers are very important. The higher the ohm rating, the less resistance it will give the amplifier. The lower the ohms, the higher resistance it will give the amp. Basically, by wiring (2) speakers in series, you can decrease the resistance (load) on your amp and reduce the wattage your amp will push into the speakers. By wiring in parallel, you can increase the resistance (load) on the amplifier and it will push more wattage into the speakers.
To clarify on those numbers, say you buy (2) 4ohm speakers. If you wire them together in parallel, you have reduced the resistance the amplifier will see down to 2ohms! That means a 50w amplifier will actually push something closer to 100w (total) into those two speakers because of the lower ohm rating! If you wire them in Series, the amplifier will see that as a 8ohm load and will actively only push ~25w total into them. That's only 12.5w per speaker, which is crap.
You can do some neat things with this - like get a dual-voicecoil subwoofer...that is @ 4ohms per voice coil. Well, wire them in parallel using a 50w amp and you can push 100w into them...it's definitely a good deal - you just upped the wattage you're pushing into a single speaker by almost double!
Your amplifier will say "2 ohm stable" or "1 ohm stable" in the specs. This will let you know how low of an impedance (resistance/load) it can handle. If you go below that level, the amp can overheat and will start "clipping" (cutting out). This is a quick way to blow your speakers
If anyone needs more clarification on this stuff, ask, I will try to explain.