Thanks to all who quickly responded.
To answer one question - I wouldn't buy from the big box stores. There is a regional family owned store that is like a HD (without the appliances) that I shop at regularly that I have a discount card for.
The cabinet supply company is a "wee bit" further drive from me, so I was wondering if it made sense to go up to them to get the MDF. Sounds like it could be. At least at the wood supply place, they have some nice Russian birch that I could also use!
The downside - it's a cash only business!
Thanks again to all!
MJ