No no no, please don't mix it. You have many distributions and Debian is usually favoured by the techs, RedHat by "newbies" and the new Mandrake Server Edition for the freaks. I'd say just improve what you are already doing good. Too many choices will just confuse people and think about your support team (handling all the OS'es).
However, I would like to see BSDi (not FreeBSD) as an option and if people ask to have a clean installation of an other distribution than RedHat this should be possible as a "flexible solution" but it should be made clear to the customer that support is limited by doing so.
Your Celeron packages are great and it can be improved by adding 800MHz and SCSI option. Perhaps an AMD Duron (200MHz bus) which is better than Celeron but cheaper than an Intel PIII. I would love to see an AMD Duron 800MHz with 256RAM and SCSI. Add the P3's as there will ALWAYS be people wanting the Intel one.
Windows 2000 is a major step from NT 4.0 Server. Altough most people/companies are slow to adapt to this technology you should be aware of the possible change in the future and what is not better to do than being prepared? Windows 2000 Advanced Server is not for everyone and it's in the word itself "Advanced"... Because of the high cost of SQL and adding IIS this is probably not going to be your sale of the day but please add it to your offerings. It might give you that width of services that others are missing.
The option to upgrade hardware without having to "pay for a new server", it should be reasonabled priced and actually encourage people to do the move instead of vice versus.
Keep your RaQ's but I would look into other solutions as well. There are actually other 1U's with "ControlPanel"'s that can be installed on a clean server overall this is a cheaper but better solution that the RaQ's. Look into Ensim (ensim.com) their server apps are excellent and creates true virtual hosting with it's own kernel etc. Yes, a bit expensive but I have noticed more and more providers are joining in so there must be a profitable case out of it. Ask them for a DEMO.