I did the same with a bike I purchased this past January. Originally wanted a Trek Roscoe 7 or 8 and had the budget for it. Local LBS were telling me a year out for these.
Found a bike that fit me nicely and upgraded to AdventX and replaced the Suntour suspension to a RockShox Recon. But did go over my original budget by replacing the overly flexy wheelset. So after selling parts my Aspect now cost more than a Roscoe 7, but less than the 8. But, I absolutely love this bike! It is exactly what I wanted. In several ways, it is better than what the Roscoe 7 would have been and maybe not as good in other ways since it's only 1x10 rather than a 1x12. But in my opinion, unless your racing, 12 speed isn't needed and requires more adjustments.
The AdventX has taken my abuse over rock gardens and through creeks without any issues.
This Fantom you bought seems to have nice wheelset, decent frame, inexpensive to replace the drivetrain and even the shox. I say go for it and sell the parts no longer needed to offset the cost. If the bike fits you well and you like it, then it's worth it.
Hint for selling your drivetrain: Sell it as a whole set. Don't try to sell it piece by piece. You will have more people interested in buying a set for a good price and will sell the front derailleur, shifter this way.
EDIT: The OP's frame is the same as this one and does show it works with a 1x system:
http://www.bikesdirect.com/products/...suspension.htm
It's too bad the OP didn't get this bike instead. Would have been less money in long run.