IA-7E is used in Japan right when we changed it to IA-7V2. They are both the same, using the same V2 boards.
You should contact us with 1) serial number of the amp and 2) where it is being sold.
All V2 boards can be upgraded to future V3 boards.
IA-7V2 is an integrated amp so what's the point of using it with another preamp? Technically it can be done but you have to do some soldering of the cables to by-pass the preamp completely. Doing that will obviously void the warranty. If you want to use with another preamp, consider the Stereo 8.5V2 which has better performance and sound quality than IA-7V2.