Yes, they are.
The WR1, like my brother has, does 0-62mph in 4.2s, 0-100mph in 10.7s and a standing quarter mile in 12.2s. It'd make your Supra look really very silly indeed.
But all turbo Imprezas are group 20 (well... sort of. Those that aren't effectively are) and, unless they have a Cat 1. alarm, immobiliser, anti-hijack system, steering wheel lock and Tracker and are kept in a locked, alarmed garage for 364 days of the year you can forget about insuring one. For £4,000 you're only going to get a problem car or high-miler grey import which will very quickly become a problem car and if you're expecting it to be "luxury" you'll be in for a large and unpleasant surprise. Unless you consider black plastic and bucket seats to be luxury.
Impreza and luxury do not belong in the same sentence, without a negative in there. And if you're worried (unjustly) about insuring an A8, you're going to have a complete eppie when it comes to insuring an Impreza.