This is good, but I highly doubt you need 8GB of RAM for an HTPC. My dad's HTPC does not play/rip/burn Blu-Ray's, but still records 1080i flawlessly off of local channels (ABC, NBC, etc). It's running off of 2GB of RAM, a Celeron (single core) 2.8GHz, and a cheapo Geforce 6200GT. Nothing impressive at all, but it surprisingly tackles hi-def video recording extremely well.
My point is that you don't need a beefy system for HD recording. Your set-up will do you VERY well, but you CAN cut some price off the top and still get amazing results. Stick with the HDD space--no doubt you'll need that (our HTPC records to our Linux server with 2TB of HDD space). 3850 will do the trick very well. Also, the E6550 will handle HD Video flawlessly, if a freaking P4-based celeron can handle it, but you could go with 4GB of RAM easily to shave some price off. Vista Media Center is impressive, so you'll have no problems there.
Again, this is a wordy rant that basically can be summed up: you don't need that much RAM.
^ Agreed, lots of overkill in your proposed system. Besides whats pointed out, you don't need a Raptor drive since the newer terabyte drives are plenty fast for a media center. Are you planing on doing any encoding? If so, you might consider overclocking to speed things up.
My media center is an Athlon XP 2500+ with 1 GB RAM, 6600GT and 2X 500 GB WD SATA drives. No problem recording/playing TV with 2 tuner cards for a LCD HDTV. I am about to upgrade just so I can use a Blu-ray player.
That would have been a good build about a year ago. The E6550 is an old 65nm chip, the motherboard is an old P35 chipset board, the new 7200RPM drives are just as fast as those old Raptors, the GPU is greatly outperformed by the newer 48x0 series, etc... Do you really need Vista Ultimate instead of Vista Home Premium? Here's a link that shows the differences between the different versions of Vista.