I don't know that you could say that it would work "as well" but I don't see how it wouldn't work. It is a compromise solution but sometimes you need to make those. Everyone I have heard of that had 170's has been happy with them so I don't see why not. Since you said you like to listen loud there would be a disadvantage that the 170 is not as efficient as the 340.
I ordered some 170's as rear surrounds last week and the scheduled delivery time is on Friday. I could maybe chuck one of them in as a center for a quick comparison to my 340 center if you aren't in a hurry to order. This would basically give me the same setup you are talking about of 340 mains with a 170 center. It would be easy for me to do a quick comparison before I get them hooked up as rears. Let me know if you are interested.
Darren
There's no place like 127.0.0.1