i know that single coils come with the hum etc. but how are you meant to put up with the increase in hum when changing chords for example.

a good example of this is srv's pride and joy, when playing the suffle and muting the strings there is more hum as you naturally take your hand off to play the 'chugging' rhythm

i can live with the hum in single coils, but its irritating have the change in amount

94' Squier Strat- sanded down (BY HAND!)

PRS Tremonti Se

Crybaby wah

Digitech tube overdrive
for lower gain stuff like SRV you shouldn't have much hum certainly not enough to be like you described. you may have a sheilding issue with your guitar. you can also get something like a Hum-X which plus in to the electric socket that you plug your amp in. cuts way down on 60 cycle hum.
Sit further away from your amp and make sure you are not near other electrical devices (computer monitors are bad for hum). You also should work on your palm muting. SRV used palm muting constantly. He played LOUD and managed to keep it under control.
I suggest noiseless pickups.. fixes everything. I can't stand a Strat or tele without them. Also, as a side note.. how is your PRS Tremonti? I was looking at getting an SE but wasn't sure if it being Korean made would differ from the American line in terms of performance..
2010 Fender American Standard Stratocaster
2011 PRS SE Santana limited edition of 25
2007 Ibanez SZ520QM-VCB
2009 Washburn Renegade WM23
Vox 20W Valvetronix