I previously posted my liking for Proto2000 E-units. I have to retract that! My initial experience was with an F7A/B, DCC + sound, and with several E6's. All run great, even with the E's m.u.'d. No complaints there.
One of my E6's I kitbashed into a Burlington E5, by simply adding corregated siding below the windows and a few other details. I didn't modify the engine room windows, which are smaller on the E5 than on the E6's, but only a true "Q" officianato will notice.
I wanted a second powered unit to run with the E5, and the Proto2000 units available were E7A/A's with a different paint scheme. But I bought them, and another one. For awhile one ran okay with the E5. But then one of the E8/9 or E7's (I forget which), burned out the decoder. Cause? Another did the same thing. Ran fine for awhile and then simply shorted out somewhere and that was that. The third ran fine for awhile and then began to derail at turnouts, and even on straight track! I checked the gage on the wheels and found one totally out of gage. I disassembled the bottom of the truck and found that the half-axle was wobbling in an enlarged hole in the gear. Temporarily fixed that, but it still keeps derailsing!!!

Caboose Hobbies in Denver can't fix the electrical problems, so I'm contacting Walthers, but in the meantime I'm having to pull my Zephyrs with the F7's. That would be fine, but the paint scheme is for freight units. (I know, there were times when that was done. I could repaint them, but they don't have steam generators. Fortunately, I have a kitbashed combine that I fixed up long ago with the steam generator section from a dummy Athearn F as a HEP car. If it weren't for wanting sound, I'd just run my Blue Box Athearn PA's chassis with the Burlington Bachman shells I fixed up long ago!