When my Roland XP-50 workstation wore out, my replacement decision was: Music Creator 6 on my laptop, Roland A-49 controller for midi input, Ketron SD-2 for my instruments, Behringer x1204USB mixer for audio. With it all connected now, I’m fighting latency. My first line of attack, I assume, is to learn whether my laptop can be expected to handle the load. All it would need to do for my purposes is record not more than 5 midi tracks, then record them to audio. The sound module being hardware shouldn’t put any load on the computer. Right? And the mixer being hardware, also no load. Right? My computer is a Dell Inspiron 9400. It has 1.66 Gz processor and 1G RAM with 61GB free space. My 10-year-old Dell w/ Windows XP running a 10-year-old Music Creator connected to my Roland workstation had no latency. So, now my question: Why is this getting harder instead of easier? Sorry. That was not my question. Here it is: Can I expect my computer to chew and swallow the potato? That is to say, is my Dell going to gag on a gigabite?

did you read my response about avoiding latency in your other thread?
 
if you insist on recording MIDI then sending the MIDI out to the Ketron then using the output of the Ketron for your audio output in that manner and you don't have a low latency high efficiency soundcard (which the behringer is NOT) then you're going to get latency.
 
90% of the latency problem is NOT the computer, it's the soundcard, its drivers and the settings you have for it.
 
when you connect it up so that you are recording MIDI at the same time you are trying to listen to the ketron all in the same system, and you don't have a low latency soundcard.  you WILL have latency.

Just buy one of these..
http://uk.focusrite.com/product-range/scarlett

Also the specific specs you list above are way too low (CPU/RAM). Consult sonar product web page for min specs, for an easier ride double them.

A good interface makes life so much easier.