Plus if you build it yourself, a year or 2 down the road its no big deal to do a full wipe, partition, reinstall of OS. Or even setup a dual boot with 2 OS's. Since you built it the first time, you have the drivers, you have the experience, you'll keep that system in better condition.
If you have more money than time, or are not willing to do the homework. Then have someone build to your specs.