Is This a good lower? Is this a good DEAL?

Spike gets his uppers and lowers form RRA. That being said a stripped a lower is a stripped lower is a stripped lower for the most part. However if you look closely , the fire control pins that most folks have there, on a Spikes hes got some sort of combo of hex nuts and some sort of retaining device. I have no idea what is up with that. You might also want to contact Jon at anvilarms.com. He sells his stripped lowers for about $100 as well.

For a home defense / SHTF rifle, when you go for an upper I highly suggest one of the following (In this order)
COLT (good luck finding one)
LMT
Charles Daly (dont know if they are making uppers only at this point)
ADS (but only if you get it from G & R Tactical cause he replaces the stock CMT bolt carrier groups with an LMT bolt carrier group)

The reason I say those and those only are: All have a 1:7 twist. They are all DI (if you want short stroke piston go for a Noveske), the castle nuts are properly staked, the gas keys are properly staked, the bolts and bolt carrier groups are magnetic particle inspected, shot peened, high pressure tested (though the Charles Daly is batch tested) and are M-16 bolt carriers, not AR-15 carriers. Like wise the barrels are all 5.56mm chambered (not wyle .223) they are also MPI'ed and HPT'ed (Chalres Daly only does batch testing). They also use milspec 4150 steel and the barrels and chambers are chrome or chrome-moly lined. They also come off the shelf with the M4 extractor spring, black insert, and crane O ring instead of the M16A2 spring and blue extractor insert.

Next would be S&W M&P line, Sabre Defense, or Armalite, uppers but they do not have the 1:7 twist.

For a plinker upper, get a Bushmaster from G&R tactical (he makes sure everything is properly staked and replaces the extractor spring and insert with the proper ones and adds a crane O ring to it). You can also go with a CMMG, but make sure you pay for the upgrades. Next would be a stag, Spikes, Anvil Arms and RRA. I would avoid Olympic and DPMS / Panther like the plauge.

Now how did I come up with this? I merely listed the rifles as to how close they follow the MILSPEC. Even the Colt 6920 doesnt 100% follow MILSPEC (the fire control group pins are the wrong size). I figured if MILSPEC has worked for how many years then you take that as the standard and select from those products that most closely follow it. I'm not saying that a Stag / CMMG / Bushy are worthless. I'm just saying that they do deviate from the MILSPEC standard in quite a few areas. Many people report that they are satisfied with those selections.

Like I intimated, your mileage may vary. I was going off of how close a rifle is to MILSPEC. You stake the castle nut for the same reason that you stake the gas key...so it doesnt come loose. If you want to remove it, then apply a little more force and it breaks clean. Good luck trying that with loctite on Oh and you are right about the castle nut. My bad. Seriously though, how many rounds do you have through your CMMG?