In terms of improving handling, there's a good amount you can do and the P80 platform is pretty responsive to change.
Delrin subframe mounts are a good idea and offer a far more predictable change in handling than a urethane insert in an aging oem/rubber type subframe mount.
Delrin subframe mounts are absolutely harder (greater shore rating) than a rubber mount. This being the case, you should consider what mounts/bushes you use in other locations.
I'd stick with a good quality oem style mount as the torque mount (lower, connects to gearbox) - urethane here will have a short service life and will have an impact on NVH.
For the lower control arm bushes, the same applies here. A decent quality replacement arm (with new bushes and a new balljoint) is ideal, a bush higher in shore here is ok but will absolutely have an increase in NVH here and, particularly on the earlier P80 cars with two-bolt LCAs, the load on the bush will mean that a urethane bush has a fairly short service life.
Strut mounts, spring seats and front swaybar links all also have a big impact on handling too.
In the rear, outer delta link bushes are the common(ish) failure, inners perhaps less so. There's no decent 'better' option here, so replace with standard.
P80 FWD cars respond well to an increase in rear swaybar size, but I certainly wouldnt increase front bar size. If front swaybar D bushes are worn, you can replace these with an aftermarket bush. I think @Drwillis detailed this in his V70R build thread for reference. A bigger rear bar will help with turn-in and makes them a more 'fun' car to drive.
In your car, I'm not sure if you have the Nivomat rear end or not but over time these get soft/squishy in the rear and you can easily replace this with the conventional spring and shock arrangement in the rear. Decent springs and shocks/struts will yield a nice improvement in handling and you'll get a small ride height drop in T-5R and R models too (using something like an Eibach or H&R product).
Happy to provide more information on any part of the above and bounce around any ideas you might have.
