I could be wrong, but because of the nature of Nebula, I have never seen a low latency Nebula preset. OwnHammer (http://www.ownhammer.com/store/index.ph ... x&cPath=13)has some awesome guitar cabs and power amps, but I don't imagine you can use them real-time with low latency. What I do is track with whatever amp-sim that sounds best that you can still get inspiring enough tones but only actually record the dry signal. Then go back (at higher latency to save CPU) and add your Nebula amp-sims and cabs. Nebula is revolutionizing digital audio, but I have not seen any presets that can be used accurately in real-time, even on a powerful computer. But my method works great and saves me the issues of trying to run Nebula at lowest latency settings.
AcmeBarGig makes good sims. the not free but very cheap ($25.00 or so)Headcase by them is actually good. For low latency ampsims I purchased Revalver when it was an Audiomidi "no-brainer" for under $50.00. I like it better than all of the much more expensive stuff. I have nice mics, nice guitars, and an amazing recording amp (Egnater), but I have been using the Revalver sim for keeper tracks recently, not just for convenience. It sounds that good when tweaked properly. I feel that the biggest inspiration killer to be the burden of fiddling with things, I can cope with not-quite-right tone. try Headcase, it's very full featured.