How much will the 58xx series cost and how much better is it than 48xx

As the title says I guess.. will the 58xx series be a lot better than the 48xx series? also how much will the new cards cost when they come out?

Going by the specs, the 5850 will outperform the 4870 by over 1.5x, as well as that, eyefinity looks pretty sweet (which I think only the 58xx cards support?). Speaking of eyefinity, am I right in thinking you'll need specific monitors to make it work? or will it work like Nvidia's 'span' multi-monitor mode (but on an obviously larger scale) where I can play Crysis Warhead over my 3 monitors.

My only reason for asking is I just RMA'd my 1GB 4870 (I RMA a lot of stuff, I have bad luck -_-) and was wondering if it'd be worth getting a £127 refund and buying a 5850. Any idea yet how much I'd have to add to that to be able to afford it?

The 5850 should be very similar to a GTX 285, maybe a bit faster, while the 5870 should be a bit faster than the GTX 295.

There is no reason that a specific type of monitor is required. A signal is a signal.