where to put rack

you mean behind the speakers,,unfortunatly my rack is 4 feet high & my suspentionless T/T sits on the top shelf.

....a question rife with double entendre possibilites, but I shan't go there.

I don't know much flexibility you have in terms of positioning the rack. But if you have a TT then you definitely want to look for the bass null. You can walk around the room while playing bass heavy music and try to find the spot at the TT height where the bass disappears.

Sidssp is absolutely right about the bass null however this does not take into account the possibly deleterious effects of reflections off of the rack on the soundstage. The best thing to do is to try all three positions and find out for yourself. You weren't doing anthing on Saturday anyway. No pain, no gain in audiophile land. You may find that the right spot makes a much bigger difference than that component upgrade you were considering. More money to use on LPs. Best of luck.

what kind of feet are on the rack? Suggestion: Buy those furniture mover pads (foam on upper side and smooth plastic bases) and put under the feet while testing it out. It'll slide around really easily for you. THen it should only take you 1/2 of Saturday :-}
aj