Stereo & Electronics - Has anybody put full range speakers in where factory subs came out??

I recentally purchased some Alpine SPS-170A speakers for my front soundstage. After thinking I have decided not to install them untill after I get a aftermarket HU up front which shouldn't be to long down the road and I have decided to pretty much replace my full system. I got to thinking about midbass and don't really like the options out there and have thought about putting another set of Alpines where the subs came out, removing the far rear speakers, and adding a sub for my low end. What do you guys think about this setup.

I got a set of 6.5 inch components. mids where the factory mids went and tweeters in the far rear... sounded really well... till i blew em up...

I never even ran any rear speakers in my old v6 camaro. just good component fronts powered by an old PG MPS2240 and a single 12" Audiomobile mass 2012 pushed by an RF 1000bd with a pioneer 7400mp HU. It sounded fine but could have used a bit of rear fill. I'm thinking of doing the same setup in my Ls1 now since I still have the HU, and sub and the factory monsoon "subs" are completely blown and the fronts are all mid range for some reason but the rear fill sounds great! .. lol.