Hi
I assume you mean Koni shocks/dampers and Eibach springs?
Sorry, no experience with these on an Alfa, but I put Tokico shocks and Eibach springs on my Ford Taurus SHO back in the USA. The SHO is another relatively heavy 4 door, albeit one with 230 hp
I really liked the Eibachs, mine were of the "progressive" type that are initially soft/compliant, but get stiffer as they load up. Some serious racers prefer "linear" springs because they are consistently stiff, but I had mine out one several road courses and found the handling fine. Since I drove about 95% on the roads, I wanted at least some semblance of smoothness (other SHO owners with adjustable Konis/linear springs report that even at their softest setting the Konis were quite stiff).
$800 sounds like a fair price - parts alone for my shocks/struts was about $600, and doing suspenion work on rusted/dirty/frozen is not a lot of fun. Get them to throw in a 4 wheel alignment/corner balance and I say go for it. Also replace all the bushings while they are in there.
I wish my rental 156 2L JTS had a tighter suspension. At the Nurburgring I was squealing and swaying while my friend in his Spider (sprot springs, shocks and 17" rims) was carving turns at a much higher speed. But then again driving on the cobblestoned streets in my town would be painful...
Kurt