multi-threaded access

Howdy, I'm involved in the development of an application using Netscape Enterprise Server 3.6 and Informix 7.22 on Irix. In looking over the release notes for ES 3.6, we noted that ES supports multithreaded access to Informix on all common Unix platforms except Irix (and Linux, there being no Linux Enterprise Sever). Moving off Irix (probably to Solaris) is an option for us, but only if there's a compelling reason to do so (i.e., only if I can make a good case to management). What are the implications of using Informix in an environment that does not support multi-threading? Our app is supporting on the order of dozens of "simultaneous" users and as it has been popular, that factor is only going to go up as we add to our customer base. We are in the midst of removing physical memory as a bottleneck by quadrupling the RAM on our machine. Is the lack of multi-threading going to be our next bottleneck? And as long as I'm tossing out questions, I've heard that it is good practice not to run servers (or other software) on the same physical machine as Informix. How bad an idea is this? Again, we could go to a separate physical machine for web servers, connected by an ample network pipe, but only if I can make a good case to management that this would produce real improvements in performance. Would it? Mark McDonough