I purchased a 21j GMTIIc while waiting on my BK Sub and surprisingly impressed with how accurate that piece is. It is keeping accurate time +/- 1 min everyday for the past month. The GMT hand works even though it is ICHS but for $135.00 it was a steal.
Now once I received my BK Sub with authentic ETA movement I began to see the difference. Side by side is the only way you can actually see the slight movement variation.
I own gens and replicas now and that 21j GMTIIc is keeping stride with my gen COSC certified watches and my ETA Swiss BK Sub. I heard they (21j) were workhorses but wow.
Either way you will be impressed with the GMTIIc build, quality and how close it is to looking gen. May need to re-lume your dial and AR the cyclops but otherwise your budget range will get you a great watch is your purchase from a AD.
Also, waterpoof it as well. My crystal was not pressed on my GMT.