As above. HDMI either works or it doesn't; there is NO difference between a $1 cable or a $100 one. I suspect the companies (such as Monster) who charged top dollar for HDMI during the early days of it's adoption were trying to cash in those people who paid big money for gold plated Scart adapters and whatnot. Hit up Amazon or wherever and find the cheapest one - you're good to go.

As for the PS3, I've always bought the lower end models and never had a problem (although I would have exceeded my launch 40gb by now had I kept it!). I've currently got a 120gb Slim model with plenty of room left. I've got a few custom soundtracks, around 15 demos, 9 full games and a couple of mandatory installs on there with plenty of room to spare. Unless you plan on whacking all your music on there, plus photos, demos and full games, you should be fine with the base unit.

As for games, you've entered the PS3 at the right time. There's 5 years worth of great games to catch up on (well, 4 years.. man, that first year.. eugh), so you absolutely need to get your hands on some of those.