I would agree with nikongod on trying a new cartridge first. I have a middle of the road TT but rather than replace it right now, I have been through three different carts and each one has had significant changes in the sound. Although I have not found exactly what I am looking for, I am going to replace my phono stage next rather than the TT.
the cart I am using is a Sumiko Talisman `S` right now. I switched about a month ago from a Denon DL103 which is considered to be an industry standard and was built like a tank compared to the talisman and the Sumiko Blue Oyster Special EVO III which I was using before the Denon.
I paid around $250 for the Denon from Needle doctor and it is a very good cart but I was looking for a bit more clarity and transparancy on the highs and the Denon is a very good Rock/Jazz cart but with my configuration it just did not get me the sound I was hoping for.
But, long story short; the cart swap outs have the biggest sonic effect over any other change I did (I had a B&O Tang 4004 TT before going with current ProJect RM6SB) and TT change was not as dramatic as cart change was.
IMO of course...
Good luck!