Got an Core i5 2400 instead today. Is memory size and speed important?
Only if you plan on using memory playback; convolution is mostly a CPU bound process. This is getting more into general performance advice than convolution-specific advice, but I wouldn't try to run (say) windows 10 with less than 4GB of RAM, and I'd advise an SSD over an HDD for the OS to avoid random I/O bottlenecks, but assuming everything is working correctly, CPU grunt is all you really care about for convolution.
That processor should serve you well based on the passmark. I actually use the i7 "sister" of your processor (an i7 2600) as my main living room HTPC, and it's more than capable for any convolution task I've attempted despite being a seven-year-old processor. Moore's Law (processor speed doubling every 2 years) is mostly over now, the processor speed gains in the last 5-10 years are not as significant as they previously were. The latest "consumer" i7 desktop sku from Intel (the 8700) is not quite twice as fast as my seven-year-old 2600, so we've gone from doubling every two years to doubling every ~eight.