I might be able to help here, as I currently run a set of Wilson Watt Pup's and power them off of a Karan KA I-180 integrated.
In a nutshell: Unless you are trying to fill a big room with 97 to 100+ db of sound, the Karan should have zero problems powering your Wilson's. The Watt Pup's are fairly efficient loudspeakers and do not inherently require gobs of transistor muscle to sing well.
I must also respectfully disagree with David12's assessment of the Karan integrated. For starters, this is the first time I've ever read or head anyone use the word 'un-involving' while referring to a Karan product. Second, the Karan is not a perfectly neutral piece (what is?). Though it is an exceptionally well balanced piece in just about every regard, it still has a character, a character that most would classify as 'dark'. I also found that the Karan presentation imbues just a touch of organic warmth. This subtle voicing lends itself very well to speakers like the Wilson's. Though the Wilson's really don't need much help in the linearity department, I feel that their lower treble/upper mid's can benefit from just a _touch_ of bloom, and that's what the Karan does for em'.
Though I agree with Krell_man's advice for listening as much as possible before buying (especially when dealing with this level of gear), I understand how difficult it can be to audition esoteric audio gear. I have damn near nothing around me, so in order to find out how something sounds, I have to plunk down the cash ahead of time. Kind of a bummer. That said, I will briefly weigh in on the other suggestions:
Accuphase amps are great products. They have a more traditional class A sound to them. Incredibly warm/organic midrange. Good detail and air, but its not a very detail oriented sound. Weighty bass thats not the last word in control, but I don't think too many would call it slow either. I wouldn't take one over a Karan, but that's just me.
Burmester makes a damned fine amp. Of course, with their entry level integrated retailing for the cost of a new sports car, thats how it should be. Though I admit to not having spent a lot of time with Burmester gear, I always walk away with the impression of them being incredibly well balanced, and sound a bit more open and airy than the Karan stuff. I wouldn't say one is inherently better than the other *unless you want to count cosmetics, and then IMHO its Burmester hands-down*, just different. Then again, take the Burmester comments with gallons of salt, as I readily admit to not being qualified enough to comment definitively on their sound.
Anyways, there you have it, from the ramblings of some random audiogoner. Before I sign off of this post, I will say this much: I'd focus your attention on warmer sounding transistor components with the Wilson's. Another good match for Wilson is a surprising one, and that is... Naim. Though Naim is anything but linear and "hi-fi", the Naim/Wilson combo works quite well. Something to consider, especially if you don't feel like breaking the bank.
