I'm in a similar boat machine wise. As it stands my PC is beast with every other task I need it for. Minecraft is the only taxing application loaded on my rig and its really not a priority in the face of the cost of upgrading.
Oh yeah. My laptop has more power, but laptops and gaming.
My PC is using parts that were the end-runs of their generation; I have an Intel Core 2 Quad that's been clocked up - it's a Yorkfield 6M, which makes it the absolute last generation before the i7, and that makes it ludicrously easy to overpower; generally, last-generation CPUs are deliberately powered down and sold at lower ratings. My graphics card is an ancient Radeon HD 4670, which is OLD, but it's a workhorse and it has a huge passive heatsink which, when covered with a spare fan, lets me do pretty much whatever I like to it.
I've run benchmarks between this old, heavily-customized beast and my flashy new i7 laptop and they come up very close to identical; the only place the desktop REALLY falls down is RAM, and you can't even use more than 4gb to run Minecraft anyway.
Now that the PS4 and XB1 are out, I'll probably be upgrading within the next year as the big titles adjust the power they need but quite frankly, if you know how to get the most you can out of the older machines they quite often trump the shiny brand new ones.