Personally I wouldn't buy any receiver thinking you will get 4K, it's too early to say if will will ever see it.Is there any point of a 4k reciever , do vm lines clear 4k channels ?
I bought the mutant HD51 because of the internal HDD, 1.7ghz processor and of course its twin cable.
I wasnt thinking of buying one i was just asking in case OP was hoping to get 4k channels :)