After reading all these post's and knowing what I have bought because I wanted something BIG, I know that after words I had "buyers remorse".
What I did learn however is that if I had a $100 to spend and I held onto it a little longer, then the next thing I knew, I had $200 and then $300. I'm starting to sound like your dad huh!
The truth of the matter is,..
With out a line in, your seriously screwed if the decks don't work or stop working!
Big doesn't mean power! There is a very good chance that thing will distort if you push the volume past 3-4-5. I know your thinking "No way!" but there are lots of radios like that.
No name radios just don't cut it in those regards.
I honestly would say, go to the Boom boxes & Parts for Sale or Trade section and look up those 20/20 boxes Sinister is selling that someone already mentioned. I have bought from him, he's a reliable source.
http://www.boomboxery.com/forum/viewforum.php?f=5
At least there you will get a box that's a performer and if you get one from him that has the deck working, then your in business, plus those have a line in (Correct Guys????)
You can do some research here on the sight, just search 20/20 and you'll find some threats. The 20/20 is BIG in dimensions too!
Good luck!