Accuracy - it really depends on what type of can you get. If you get an old style MAC can with rubber "wipes" you will have some degredation in accuracy. As the bullet passes through the can, it punches through several thin rubber walls (ie the wipes). When these touch the bullet, they will slightly deflect the bullet. Of course, these types of supressors were mostly used only on MACs, so its not like there was any long range accuracy in the first place. Most cans these days have no wipes, but metal walls and baffles. The bullet will pass through the hole in the baffles and not touch anything so there's not much of a degredation in accuracy. I'm sure there's a little but it shouldn't be too much.
I'd recommend looking at Gemtech (www.gem-tech.com) They make first rate stuff, and their customer service is second to none. If you ever have a problem with a Gemtech, you can count on Doc Dater to set it right. The Gemtech stuff is pricey, but it really is top notch - its pretty much the Mercedes Benz of supressors; expensive but you get what you pay for. Their stuff is great.
AWC also makes nice stuff, but from what I've heard, their customer service is awful...unless you're a large police department and they're afraid of losing your account. Some people will say they've had good service with AWC, but in almost 10 years of dabbling in NFA, I've heard much more bad about their customer service than good. Not that their stuff isn't good - it is - but I'd want to know the manufacturer is going to back up his products.
There's also a lot of good quality stuff from small manufacturers - I could probably recommend some more. It really depends on what you're looking to put the supressor on. What gun (or guns) are you planning on putting the supressor on?
...and just for full disclosure; I don't own any supressors, so I don't have an axe to grind. But after almost 10 years in NFA stuff, I have shot lots of them and talked to many owners.