x58 at this point is still a strong chipset, but there is not only a single replacement since then...
You are correct about Sandy Bridge replacing it (P67, z68) and it's big LGA-2011 brother (X79)
But... that was replaced by Ivy Bridge (Z77)
and now the new Haswell (Z87) boards are starting to appear for the new chips coming out in the next few months.
So, while it is still a solid platform, it would probably be better to wait for the price drop after Z87 comes out, and get Z77 or just go all the way and get a Z87 system
Thank you for your answers I'll consider that motherboard, seems a good one
I will add that Haswell is rumored to be arriving this summer. If you must then upgrade, but judging from your 920 you would be wise to wait, as Haswell may introduce newer better chips and at the very least reduce the price of an upgrade, or give you Ivy Bridge options in your price bracket.
Thank you for your inputs, I've decided in buying a x58 mobo, since I just need a mobo that allows my 920 to unload it's true potential, which will last me some good years, and wont be a bottleneck to the future GTX 670 Power Edition GPU.