Unless you can get $300 on a private sale (or craigslist?) I'd grab it. I looked on eBay and saw a couple of M1300s but I really don't know what to make of the pricing.
Over on the West Coast I'm seeing well equipped M1400s going for closer to 800-1000 but that's pristine condition with a gig of ram and 60 gig internal drives and hard top keyboards.
What are the specs on your M1300?
What do they want for the LE1600 and how is it configured?