You don't need to spend £1200 on a computer to get a "top notch" one for flight simulator - I got an HP HD connect laptop for around £700 - and is very good for flight simulator - can be conencted to HD TV if you need larger screen.
Had high specs and very good with flight simulator software.
If it helps? For IR training - I would think a little - it's about instrument scan practise - however the controls in the sims are the biggest problem!