Right there are no Flashcarts for the PSP. PSP uses a Custom Firmware (CFW) hack which allows it to run ripped ISO's etc off a memorystick and run unsigned code (e.g. allows homebrew to be used) etc. I would advise not getting PSP-3000 at the moment as this model is unable to have a CFW installed. The process of installing a CFW on PSP is tad difficult. To keep it easy for you I would advise just buying a 'Pandora Battery' and 'Magic Memorystick' from DealExtreme or any reputable electronic site which deals in these area's, as it makes the process easier and less daunting for a new comer to the scene.
The last digit of the PSP 2000 (2001, 2002, 2003, 2004) is simply the region code....you're implying by the above statement that only European PSP's are getting the newer mobo's in their slim and lites, which is incorrect.
First, it is near impossible to find a hackable PSP thats new. I bought two PSP slims thinking that at least one would be hackable, but to my despair, both had a firmware over 4.01 (Meaning that they both have a TA-088v3 motherboard which is unhackable). So if you want to buy a PSP that you can hack, buy a used one with firmware BELOW 4.01. Also, in order to hack you will need to buy a Pandora's battery which will put your PSP into service mode and allow you to install a CFW.