I have spent loads and the best router for ADSL I found was a £10 ebay BT 2700 smile
Did you know they do a fibre version of the 2700 ? In fact the latest versions do both DSL and VDSL.
What will please the engineer most, will be easy clear access to the NTE, and the required spare power supply all ready and waiting.
If you to ask for a D-side measurement, as soon as they get off the phone, unplug your current DSL kit as it can make taking a measurement a little trickier at times. Hover over the engineers shoulder when they run the test with the JDSU/Exfo, and ask to make a note of the stats at that point. It might be noted that the modem will usually produce a slightly hgher sync rate than the test kit.
Ask if the engineer is fitting one of the new updated modems, and ask that they wall mount it.
Good luck.