Name's Six (yes, real name) and my first ever tube amp (that actually worked, long story) was a rack rig with an MP1 in it. Bought it when I was 18 for $250 at a pawn store with the MP1 and a Marshall 9005 power amp that weighed a tonne. 10 years later and I may not have the awful carpet covered rack or back breaking 9005, but the MP1 still lives in a rack at home. For years I used it with a Triaxis and a Simul 2:90 in a rack controlled with a G System to switch between the pres and control everything. I held onto it forever because I am a HUGE Type O Negative fan and could nail Kennys tone from the first 3 albums because he used the MP1 for those records.
These days however it lives in the rack on my production desk above my Torpedo VB101 ready to be patched in and belt out some recordings. Soon it will be joined by an MP2 I bought today once I get it in working order.