I would rec. against buying a used PS2 (unless you know who you are buying from and the history or the machine..)
If you buy a new one you will probably get a V7... You want to try to get a V5 or above... The sticker on the back of the PS2 has a number that looks like this: SCPH-xxxxxxx try to get one with a R at the end of that number(but be careful, there are some V4's with a R)... The website I usually refer people too is currently down... Should be up later... I'll post the link later so you can see EXACTLY what I mean... It has all the info you will need as far as "what version the PS2 is that you are going to buy"
The best mod chips to get are the NO-SWAP chips like the Messiah, Magic 2, or Apple... They are more expensive to purchase and have installed BUT are worth EVERY PENNY....
Your CD-R backups of the PS1 games will work on your PS2... Also you can use PS1 controllers on your PS2...
