I just installed a Pioneer tape deck I had laying around. I didn't have to cut the dash. I did have to install the face plate, and you can see a small portion of the indent around the old tune and volume knobs. Impala Bob's sells these and a Kenwood unit that has been modified to fit our dash. Both of them are less than $300. The cheapest kenwood is $220. They both have RCA Preouts for whatever amp you would like.
I see the radios in my catalog, but don't see them on the website.
http://www.impalas.com/
I've always thought Custom Autosound was a bit on the cheap side with their products. Not inexpensive, CHEAP.