I found the following instrumental bands/albums interesting at different times:
- Don Caballero
- Russian Circles
- Agalloch - The White
- Chimp Spanner
- Drudkh - Songs of Grief and Solitude
- Blotted Science
- Green Carnation - Acoustic Verses
- Scale The Summit
- Gordian Knot
- Mouse On The Keys ( Not metal.. )
- What the Blood Revealed.
- Behold The Arctopus
Not sure if this what you are looking for.