what impacts the sound quality more amp or pre-amp

I think a high quality sounding preamp can carry a mediocre amp and visa versa. But without question you will want to eventually upgrade any other inferior component(s) to get the desired sound you are ultimately seeking. I would tackle the preamp first since its job is the toughest and it is one of the hardest components for a manufacturer to get right. To find one that sounds decent within a certain budget can be difficult but not impossible.

A few years ago I owned some B&K components & liked them but found out that some of their models stand out more so than others in terms of sound quality. That would include some of their older gear.

Everyone is correct and its obvious they have all had vast experience in this hobby. If I were you I would upgrade my preamp first, you might look at some used CJ like PV10 in particular.

You get a real bang for your buck and you get very tubey sound but totally grain free and non-fatiguing. Just an option.

Dvdgreco, if your looking for advise on the best bang for your buck system improvement, why not post your system? Be careful of advise touting personal technology preferences without considering your personal budget and system.

my system is

B&K ST202 (I think its a sonata series??)
B&K 10ProMC
Alon II speakers
Jolida 100 cd

Are you sure that you want to rule out an integrated?
Personaly, I don't consider separates unless I am prepared to spend thousands, at least couple of them.