I have a 520, running a lean 8.1 well with 20 MB of RAM. If you have a choice, look for another PB series than the 5xx. WiFi capable equipment would be far overpriced. A lot of 5xxs have an issue with the one external serial port. If I had to pay for one I would go for a top of the line 540/540c, as you probably would not like the screen of the 520 compared to recent computers. If you sticked with 7.1 just for liberation, the 180 might be a good choice. If you want to have an old laptop machine fitting into present work environment, you might look for a fully started up 1400 (not exactly a 68kM, but one of the finest PBs Apple made).