I did something similiar. PPL-ASEL, 15 hour Multi-Add on, then started IFR in the Cessna and finished it with the checkride in the Aztec. Checked both blocks and took a good chunk out of the 100 multi that seems to be the mark now.
I would advocate getting the multi-time early. Everyone has been saying to get the MEI and get a twin student, but those are few and far between. I say get as much as you can while you can then worry about building TT as a CFI.