You've made no mention of what Computer Platform/OS you are on, processor speed, amount of RAM, hard drive speed, DAW that you are using, etc. All of that could be determining factors. I personally have no load issues at all when previewing sounds in Spark.
Are you saying that your spark is auto-previewing sounds instantly as you select them in library pane? No 1-2 seconds "loading" or any delay whatsoever before you hear the sound? That would be strange, because for me spark 2 (i have software only) has exactly the same sample loading time in cubase 7, live 9 and standalone, both on windows 7 and osx 10.9.5, on any given audio interface whether it is professional or a standard audio controller. So unfortunately this most certenily is not a problem with my daw, os or hardware.
The 2 seconds that spark takes to load a sound is very unusual among plugins. I am guessing that its due to poor programming, and probably an effect inside spark, like reverb is causing this unnecessary loading time. Spark is not a heavy plugin so it should not be like this. The main problem is, that it prevents you from audition sounds quickly and I am used to auditioning samples way quicker then spark is letting me.
Normally, the way I use Spark, I've usually only load the full kits which takes about 1 full second for me. But just to be sure I wasn't missing something, I just now went into the individual sounds of the Library with "Auto Preview" checked and used the down arrow key on my iMac's keyboard to scroll down through each sound... with each sound instantly loading and previewing/sounding (no more than a half a second, if even that.)
So again I ask, what are your specs. I use to work tech support in this industry, so I know what actually matters (and I'm just trying to be helpful, I no longer get paid for this sh*t!) For example, and be honest here, are you running your DAW in 32 bit or 64 bit mode? And how much RAM? Processor speed? And how about the speed of your hard drive, what is the RPM or are you using an ssd? It may make more of a difference than you imagine. As for audio interface, etc., I'm only using NI's Komplete Audio 6 as my audio interface and the latest version of Ableton Live 9 Suite on OS X 10.10.3.