NEWBIE Informix product advice

We have a DOS/Clipper application we are considering rewriting. We are in need of some advice, as to which Informix product would be suitable for our needs. For the back end, is there an NT product? Is it stable? There are remote offices connecting over a slow WAN that need access to the application. Would it be better to set up a UNIX box, and telnet in? We are leaning towards an NT solution due to previous experience with the OS, but want it to be stable, and be remotely accessible. For the front end, we do not particularly want or need a GUI interface but it seems to be a requirement nowadays. If we go GUI, is there any advantage to using Informix's tools vs. Powerbuilder, VC, or VB? Would a GUI interface running on a Win95 machine accessing an Informix database on an NT server be slow over a WAN link? Or does it matter? Are the front-end development tools difficult? We have experience in Clipper, VB, VC++, Access and about 20 other batch and scripting languages. Any advice would be appreciated.