Carver M-500t Reconditioning

My mid-80's Carver M-500t amplifier is in need of reconditioning and I was curious as to whether anyone has any recommnedations as to whom does this type of work. So far I have contacted:

1. Carver MKII mods
2. Rita's Vintage Audio
3. Carver Audio Repair

They all seem pretty reasonable - but I have no context by which to judge their work or make a decision.

The expert help of the Forum would be greatly appreciated!

Thanks.