Re: time for a change....
only one descison really, auto or manual
take a look at the spec sheets and the pre-2001 cars arguably do not have tremendous specs by even a 02 plate 156, but it's also the quality of the toys that count. Yes eg the 156 has a premium sound system by Bose, but compared to the standard 166 is not that great, likewise the aircon on a 166 is not split level like a 156, but it works a treat, the leather is proper Momo leather not some plastic coated stuff. Bear all that in mind and you will not be disappointed.
Things to watch out are the usual cambelt and suspension stuff really, make sure it has a CD player, Satnav and phone if it's advertised as such. Just because there are buttons on the dash, it does not mean the unit is fitted, they are all 'enabled', just not specced. Check out the left side of the boot for the goody count, ideally you sould see from top to bottom, DSP amp, satnav, CD changer, and if really lucky a slot in the dash for the phone.
Next choice will be colour in and out, silver most common but other dark metallics work well.
Finding the right one will be the biggest challenge, by the time you have set your price, decided on mileage, FSH, transmission, colour and interior colour, wheel type and sound sytem, the car will not exist or it will be 300 miles away.
HTH and good luck