Well with a dead DFI 790FXB I'm faced with a dilemna and a missing motherboard. Personally I liked the DFI board although I only bought it in the first place beacuse it was the only 790FX + SB750 motheboard available at the time and at £120 it's now only £10 cheaper than the ASUS M79A-T. I've also read that the future Phenom II processors are designed for a 790GX "Dragon" platform. Should I bother with the GX boards? Anyway I will probably need a new motherboard for my 9850BE so if anyone has any advice.
I LOVE my M3N-HT Deluxe, but I don't know about the new platform - I would like to use this board with a new X4 950 this Jan (I believe that will be an option, correct me if I'm wrong). If you just looking for a solid board to run your 9850BE then I'd recommend the M3N-HT - for the record I'm also using a 9850BE.
According to Expreview the Dragon platform is 790 series + SB750 along with a Phenom II and 4800. http://en.expreview.com/2008/11/18/amd-dragon-platforms-plan-and-performance-exposed.html
I would say that as you have an AMD / ATI GPU that you’re going to be better off keeping to the AMD / ATI chipset. The ASUS M79A-T I've heard some good things and seem to have gotten the claim to be the best Phenom clocking board but time will tell. The M3N-HT Deluxe is also not currently listed in the Asus AM3 Support list, I would hope it will be added soon being one of the most high end Nvidia AM2+ Boards but it’s not currently. List Here: http://event.asus.com/mb/AM3_CPU_Support/ I think that with the next gen AMD CPUs looking so promising that support for them is a good upgrade path.
The only problem with the ASUS M3A79-T ATM is that it's £140 while the DFI 790FXB and GX are both sub £120.
What about Gigabyte's MA790X-DS4? I saw one yesterday for $160AU, so they should be pretty cheap in pounds. I've heard nothing but good things about them.