If I may, you should consider this particular Arsenal model: http://www.arsenal-bg.com/defense_po...,62sar-m9f.htm
This is a same rifle, modified by a friend of mine in Bulgaria... He changed only few components, bottom line price ( except the optics), simply because he didn't need more from the rifle, but it is outstanding model, here is the picture of his actual rifle, full size so you can check details if you're interested:
I understand that you're looking at SBR model and this is ful size rifle. I don't know the exact Arsenal model for the SBR version, but this is basically the same receiver, same rifle in SBR size, that I had a chance to hold in the last year's SHOT show in LV, these are my picture and video, I asked one of the by-standers to operate the safety for me, it is absolutely great IMHO, works very smooth and convenient for right strong hand:
Here is the short video:
I am not a huge fan of the caliber, but the rifle is outstanding, I don't remember if they had it in 5.45, I believe the milled receiver is only for the heavier classic 7.62 AK caliber, but if I go for SBR AK, I think this would be my choice...