I don't know what a MOTU is, but I love Grados and the 80s were the first Grados I picked up. I completely fell in love with them, and I like my 325s ALMOST as much as I like my BeyerDynamic T1s, which are over three times the price.
Anyway, I don't know if this helps cause I'm not sure what specific gear you're looking for, but today I took delivery on a Little Dot 1+ tube hybrid amp to use specifically with my Grado 80s in the bedroom and I'm blown away by this thing so far. It's made specifically for lower impedance cans like the Grado line. The build quality and early impressions of sound quality are fantastic. An inexpensive DAC (I use an audioengine D1) into the LD amp and you're in for a real treat. If you love the Grado sound so far, I'd encourage you to stick with that line cause it's hard to find that same type of sound in other headphones. I already know for certain I'll have Grados in my house for many years to come...I love em

Anyway, Little Dot has a nice line of products and the customer service has been excellent. They have DACs, amps, and other tube gear that comes along with an excellent reputation. Just another option for you to consider in terms of budget conscious gear

EDIT: Actually, for the 80s, the headphone amp on the Audioengine D1 DAC sounds great...I was playing around with it last night and it's really all you need for the lower end Grados. Just plug the D1 into your laptop, plug the Grados into the DAC, and you're good to go! Sounds fantastic
