What to upgrade next?

Yes we are in the process of changing our generic entertainment center to a custom walnut slab unit. Not necessarily specifically made for audio but it is very solid and wifey approved. The TT came with 3 point isolation pointed feet so hopefully that is correct isolation. I thought about the Zu version of that cartridge but they were out of stock a while back when I was looking into it. I've since come across SoundSmith and was wondering how much improvement that brand might bring in. I can move the speakers around a little bit but the location in our room is a bit limited. 

Rick

What I am looking for is better separation and clarity and dynamics from the upgrade.
Yeah I forgot to mention the phono stage I am using is a PS Audio Nuwave. You just never know where the weak link is until you try something else. 
If i do decide to replace the tubes, I am pretty sure I will go with the KR300b HP. It's supposed to be their high performance tube made with top notch parts. 

Wow Aintitgr8 that makes sense. Maybe that's why I can't hear any difference between the $35 and $750 I.C.'s. I also tried a PS Audio AC12 power cord and there was no difference. The speaker cables I have are Zu Mission with the BU3 connector on the speaker end for a good solid connection. Maybe an upgrade to Zu Event may help or yet another brand of speaker cables. It's so hard to really know what is the bottleneck in the system.