Hi everyone - I'm a 'lurker' who, until now anyway, only George knew! (My name's Mike BTW.)
Phil - reading this thread has made me 'come out' because hopefully I might be able to help you a lot by relating my experience because it's IDENTICAL to you!
Like you, I was pretty wary of Win 8 too, having been an XP man for years. Like you, I looked into upgrading my existing machine. In my experience though, I'd seriously think about getting a new computer if you can afford it. Older computers just can't take the RAM you really need. They say 'a minimum of 4 GB but Win 8.1 is far better with much more – probably at least 8 GB.
In Jan, I got a new PC with Win 8.1 installed. + believe me, it's great - it's so much quicker. In fact, today, I've installed an update that makes it work even better. Forget all the horror stories about Win 8 – Microsoft made the whole thing a lot more user friendly for people like us in the Win 8.1 upgrade. Forget the Start screens etc. too as you don't have to bother using them – I haven't. You can boot straight to a desktop + use your new machine just like you're used to except everything is much quicker.
I was using MS Money on my old machine. I got Bank Genie Pro and it works perfectly with Win 8.1 and I'm using 64-bit. I imported all the data from MS Money + off I went.