if the white sox can continue playing hot baseball, buehrle might be the combo of the best pitcher with the most wins and the easiest to get. he won't give you Ks, but with the sox solid offense, he's good for 15 wins.
mulder is the best pitcher of the lot, but depending on situations, he's hard to get. unless he doesnt shake off his early season problems, he's also 15-20 wins.
david wells has been pulling magic out of his hefty arse, i'd say 3.8 era and 12-17 wins.
clemens... hmm. 15 wins, 3.5-3.7 era? never liked the guy much.