I was also tempted by a 159. Dutch Bas came to LMC in a tuned 159 GTD a few years back and I was very impressed. Build quality is supposed to be improving all the time, and to be honest, most cars have trouble with clogged EGR valves. At the end of the day it's an Alfa, be prepared for a slightly tempestuous relationship and you won't be dissapointed. Expect VW levels of refinement and reliability and you are just setting yourself up for a fall.
My personal experience of Alfas has been all good. The cheap rusty Suds and Sud Sprints I ran in the early 90's were all pretty reliable in the fact they got you to where you were going, if you ignored the non functioning sticks and switches behind the steering wheel. The high miles 156 Selespeed I smoked around in for two years was also spot on despite plenty of abuse, non existent servicing and upkeep- only needing an air flow meter replacing. Not bad considering the £200 I paid for the car in the first place.
Last but not least are the Giulias I've owned. Simply the finest cars I have ever driven. Achingly pretty, beautiful handling, a gem of an engine and super reliable. A Giulia Coupe is the only car I've ever done a 700 mile journey in and wanted to carry on going. I love them to bits and they have probably kept me sane over the last 5-6 years. No matter how bad your day, just five minutes in a old GT and your troubles just melt away.
My advice would be to go spend £500 on a shitty diesel Mondeo for life chores, and spend the £25k on a really nice 1750 GTV instead. You won't regret it.