Upgrade advice

Hi everyone,I am thinking about jumping on the i7 bandwagon, as everyone seems to be raving about how good they are for FSX... I currently have an E8500 with 4Gb of RAM and a GTX250, using Windows Vista 64bit. PSU is an Antec 650W. The CPU has a Shuriken Scythe cooling fan. The mobo is an Asus P5E. Nothing really overclocked, but I can't run sliders up very high and I get stutters and pauses. I have followed Nick_N's guide so it runs pretty optimised. I am thinking about an i7-975, Asus P6T mobo, 6Gb of 1600Mhz 6-6-6 (hard to find) or 7-7-7 RAM, with the same PSU. When W7 comes out I will upgrade to that. Is that a worthwhile upgrade? I'm looking for an improvement in smoothness and sliders not necessarily uber-high frame rates.Will my current GTX250 work with this combo, or should I get a 285 as well? The 285 cards are really long and won't fit into my case, so then I'd have to buy a new case as well :( What does everyone think?Jonathan