Well, you already think you are doing well at SNGs, is that correct? And you want to move to higher limits as you gain a bankroll?
From what I can tell, although I have not tried higher priced SNGs (the highest I will play is $20 but I have watched the higher limit ones play out), the aggression factor goes up rather dramatically as the buy in gets greater. A low levels, SNGs are pretty soft -- full of weaker looser players who pretty much spew their chips on lesser holdings. The higher you go, the more sharks you run into. Fewer people play in each hand. The pots tend to be bigger. The higher the buy-in, the less likely you will be able to limp in to any hand -- nearly every hand is raised.
So not only do you need to adjust to the stronger play, your bankroll should probably be a bit larger in relation to the buy-ins, as your results will likely be a bit more swingy.
My personal aversion to playing at higher buy-ins has to do with my own comfort zone. And my current BR...
Whatever you play, do use good bankroll management, so that the inevitable downswings will not bother you too much.