interconnect ?

I have been involved in audio for about five years and have a question that has been really hard for me to answer. Where do people think you should have your best inconnects. I know some will say they should be all the some but some of us do not have the luxury to afford all of the best.

Is it better to put the better interconnect between the pre amp to amp...or would it be better from the source to pre.

I am currently running an older audio research d-60 amp, adcom gsa 700 pre processor, sony dvp s7000 source. Cables to play with are mit 330 plus ( 1m length , and mit t2 (2m legnth)

I have switched it over dozens of times and can easily say the sounds are different, but I have a really hard time deciding which sound is better. Wondering if anyone can help.
Considering a CD/Pre/Amp/Speaker setup, general wisdom would say that here is the order of priority:

(1) Source to Pre
(2) Amp to Speaker
(3) Pre to Amp
Being that you can't afford more than one piece.I would buy the best common size ( 1 meter etc. ) interconnect I could afford ( that has exceptional reviews ) and place it on whichever peice it sounds best . Also your considerations should be with a company that has a return policy...
When I had seperates I achieved the best sound with the best IC (AZ Mat Ref MKII) between the pre and amp and the lesser IC (AZ WOW) from CD to pre. It had more control and extension and was more neutral to boot. It was surprising to me as I expected the other way to sound better but that was mushy in comparison.