The KT133 system is probably running just fine for what it does, right? So I would replace that NF2 mobo with the faulty RTC. Hopefully getting a whole new mobo will fix that problem, but what's this about hibernating through the serial port? The NF2 Ultra 400 made some nice upgrades and fixes to the standard NF2 chipset, but I don't use hibernating so I can't comment on that.
In the end, it's better to keep your high-end system high-end, and just upgrade your other systems occasionally. I mean really, how much power do you need to surf the web? Just about any old PC will do.