Phil
Companies with 3 aircraft have used Acrobatico, and some with 23 aircraft have used it. Not sure what you mean by "simplistic" but I'm sure the likes of Monarch and Excel find it a very good package having endorsed it for years. Having used it myself in the past, I too found it a very good package.
Anyway, good luck with your project. I agree that Acrobatico won't provide the quoting aspects, but then any good XL spreadsheet will do that !!