Early DSA guns with the surplus parts were and are great guns overall. I have had mine for years and it's one of the earlier guns when they were not offering as many options , Maybe mid 90's?
Current DSA guns are still great FALS and some folks may think they are sub par to the original parts guns and they could be. However, I have seen little in side by side shooting to show me that they are indeed sub par.
On the Century and Enterprise guns , they are kind of crap shoot from fantastic to just ok and may need some work to get 100%. Some of the century guns may look like crap, but are decent guns and most of the time they can be bought for a lot less then a DSA gun. Even if the gun doesn't run the best, you can rework the parts or send it to a number of guys to fix.
Another option is too look for a SAR48 from Springfield. Occasionally I will see some of these go for under $1500 and they are great guns.
Good luck