I hate to say this on a competing forum, but check out Reverend Biker's suggestions on lowering the 650 on V-Strom Riders International website. Lots of other good information on the Stroms both big and small as well.
I have the big Vee and really wanted the little Wee when I bought mine, but I was going to have to wait for the Wee and the price of the Vee (an '06 carryover) was virtually the same as the '07 Wee with ABS.
I weigh 260 on a good day and the Vee has WAY more power than I can use. I have absolutely no doubt that the Wee can handle your bulk. And yes, they do come with a lower seat than the Vee, but swinging your ol' leg over the beast will be the same whether its the 650 or 1000 - they both use the same chassis and wheels. For some reason, though, the Wee is about an inch longer in wheelbase than the Vee.