You still have $200 left over for a decent sized memory card, some rechargeable batteries (K-x uses AA sized batteries, please use something decent like the Sanyo Eneloops that have a long charge retention) and a dry box or cabinet.
The tripod can wait, tripods can last you a long long time and it would make sense to invest in one in the future even if a $200-300 tripod sounds expensive to you at the moment.
There's nothing wrong with 2nd hand lenses, just make sure they work well and come fungus free.
Definitely, you'll find that the 450D and 500D both fit somewhat into your budget though 500D will be stretching it tight. Also the 550D is about to hit the market, probably just a couple of days away so if you wait just these few days you can probably find people ditching their 450D/500D for the newer cams and you might just get a good offer for one. Try to get a bundle where people throw in things like memory sticks, extra batteries, kit lenses and so on. These are more or less essential and often when people sell their gear they don't include the costs of these so it easily translates into an additional $100+ savings compared to getting it new.
Welcome to CS You can try handling your friend's cameras & ask them why they bought their camera. From they get a feel of it in your hands. If not, just drop by the shops & do the same. You don't have to buy the 1st one you see. Read up on some reviews & consider before taking the plunge
Yup. Learning. Took some pictures at universal studios using my fren's cam ytd. haha.
Its interesting. Most prob getting 400D. Fren say its good enuff for a newbie like me. Thanks for all your advices.