There are many people here that have the same and quite vaster experience, with users, hardware and budgeting etc. I ran a whole department for 84 users once and was the ONLY person in the there, I did administration, management and tech support, just me.
They had 1 (one) 450p3 desktop running ALL there services (domain, ftp, smtp, dns, proxy, http, sql and a couple I forgot). IDE mirrored RAID (teehee ...) and 256mb of ram while it ran at well over 600mb, thus paging fiercely.
Off topic, I also stick to things that work, mainly OpenBSD for my services (except the odd one that requires something special), nobody here said it was the only OS they use ... Most expericenced admins or developers and other such persons here also have much experience with other peoples shoddy work and having to "deal with it", especially when Murphy is watching, like you said in front of a "potential 500k customer".
So, my opinion is, use OpenBSD, if it does not have it (yet) you dont need it, also use USB on OpenBSD, it works too
