If you currently have PS2 games, buy a PS2. Refurbs (Fats and Slims) are inexpensive. If you wish to play backups, obtain a method to load homebrew (I recommend Codebreaker 9 or higher) and use FMCB+ESR (plays backups of domestics and imports) available in the forums.
Fat systems are more versatile. You have the option of internal hdd and fewer compatibility issues with USB thumb drives.
PS2 v7; non-mod
; SONY BBA; Segate Baracuda 160GB HDD <FMCB 1.8 / ESR .9b on MadCatz 8MB MC>
PS2 v4; non-mod
; SONY BBA; Hitachi 60GB HDD (Failing lens
) <FMCB 1.8 / ESR .9b on Official Sony 8MB MC>