A lot of suites just have one bed for that reason and you may be hard pressed to find a suite at a large Strip hotel with more than two beds in it.
I think Planet Hollywood has Panorama suites which have three couches, 1.5 bathrooms and a bedroom, and then you can get the connector for an additional fee with another bedroom. You could be pushing it with 6 people in the room though for housekeeping etc. Without the connector the room goes for as low as $389 a night but is generally around $589.
Try the condos that are around the Strip. MGM Signature suites and Wyndham Grand Desert are either on the Strip or near it, and have multi bedded rooms for decent prices. Browse eBay for Wyndham or
www.vrbo.com for MGM for cheaper rentals.
My friends stayed at the Wyndham for $100 a night (via a guy on eBay) and there were 5 or 6 of them in a huge 3 bedroom suite.
There is also Platinum, of which I've read good things. They have two bedroom suites as well for decent prices and lots of room it seems.
http://www.theplatinumhotel.com/guest_suites/suites.asp I think the Marquise room would fit 6 people if some slept on the couch.
Or just get one of the Fantasy Suites at the Palms. They have lots of room and beds...but start at $2500 a night if I recall correctly.