[Coda]

If you're buying a motherboard you're getting really close to being better off buying a new machine.

I'm also uncertain that an upgrade from that particular i5 is even worthwhile -- that is a solid CPU that should give you AT LEAST another year of useful performance before it starts feeling too slow.

Upgrading a motherboard provides very little benefit on its own. The motherboard mostly only provides an interconnection between the components of your system as well as some baseline functionality that doesn't really change from mobo to mobo. (Most motherboards provide roughly equivalent audio, networking, and USB.) The only reason you'd want to upgrade your motherboard is if you get a new CPU that doesn't fit in the old motherboard's socket -- try looking for a CPU that fits the socket you have.

And even then you won't gain much from a motherboard update if you're not also upgrading your RAM, because newer motherboards benefit most from faster RAM. (If you're particularly unlucky your existing slower RAM won't even WORK on the board.)

Meanwhile, new computers these days are getting CHEAP. You may well be able to find a complete new computer for not much more than just the parts you're looking at upgrading.