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Well the 995 and the (original) 8500 are probably near identical in detection range, the X50 probably has a good edge over both of them in K band. With that said many users on here (Audi-Quattro & CrazyVolvoRob come to mind) have Vector 995's which it seems from their posts they were more then pleased with.
If your on a budget, and really can't squeeze out the 300+ for the Top 3/4, the Vector995 should give you near identical range, and a lesser cost.
I wish the X50 had a slight edge on KA....... It seems to have tunnel vision with KA band.