I've had very good experiences with AOPA - US Alliance for financing my 170B.
When they came up with a Vref value of 39K and knowing it was worth WAY more with all the modifications, they located and recommended me hiring a certified aircraft appraiser who was able to put an accurate value on the airplane making numbers for the loan work out to my benefit.
The appraisal was $600 but exceptionally thorough,12 pages of addressing every possible aspect of the aircraft condition, modifications and logbooks and money well spent.
