When you say "newer models" are you referring to the remote of the DVD player?
I don't know if the AV703 uses the same signals as the AD600A, but if it does, you can program the Prod 8 to work it. I haven't had a chance to write up "step by step" instructions for the Prod 8 but essentially you need to perform the same steps as you would with the C7, it just that the actual commands are different.
If you print the step by step instructions for the C7 and then print the P8 manual (both on my site), you should be able to figure it out.
For instance, the first step is to re-assign the DVD button to be a TV button.
On the C7, you would do this...
[SETUP **] 992 ** TV DVD **
On the P8, you would do this...
[SETUP]
scroll to CONFIGURE
scroll to MODEMAP
hit TV
hit DVD
escape
It would be a good idea to do a test before you do too much work. Assign code 0030 to the TV button and press the POWER key, if the 703 code is the same as the 600 you should see the volume up indicator display on the screen. If you don't then the 703 probably uses a different code.
If any Apex 703 users would like me to find out for sure what codes their DVD uses, I would need to borrow your actual Apex remote. If you're interested email me.
Rob.
http://www.hifi-remote.com/