The HTM7 is a nice center and the 703 is in their mid-range but uses their metal dome tweeters where the newer models of the 600 line uses their aluminum speakers. It is something B&W did after the 703 was developed to provide a low entry point into their speakers.
Matched with the right components and amps, I'm sure you are happy listening to them or you wouldn't have bought them. Yes, the 800 series is 'higher end' but everyone has a budget and the idea is to get the best system sound you can from the money you have to dedicate to the sound system.
Hope this helps. Ignore the other guy. This is ALWAYS soemthing better no matter what you buy.