Reliable but affordable SFP aggregation switch?

Hey Gang,

I do some work for a small ISP who deploys a free service sporadically across the city. Due to it's widespread sporadic deployment, everything is fibre based. It's historically a Cisco shop but starting to branch out a bit. We've been using repurposed old ME3400s for this free service but have found some odd traffic behaviour, lots of dropped frames and unreliable performance. From what I'm told, it just an old buggy platform.

They have expensive routers for paying customers but reluctant to eat up ports on these for the free service. Perfectly happy to spare 1 or 2 ports to trunk down into some kind of aggregation switch, but we still need the SFP based interfaces for all these last mile fibre connections. Wondering if anyone can recommend an affordable platform that won't kill me on support/frustration :)