Upgrade Question

I'm looking for suggestions on what you think would have the best bang for the buck for my next upgrade. Current system consists of ARC ss 100.2 amp and LS15 pre, B&W 802 matrix III, Linn Ikemi and modest cables (Tara Ref Gen ICs and Audiodyne silver speaker cable). I'm due for new tubes in the preamp, so changing from the original tubes can also be thrown into the mix. Upgrading from the Rega Planet to the Ikemi was huge and I'm looking for a similar impact on my next move. Thanks.
shunyanta power conditioner ,cleans it all up
Get a nice power cord for the digital source. Spend $550 or so on a used Virtual Dynamics Nite AC cord, and you will not beleive the positive sonic impact it will make on your system.

I've read multiple posts that claim power cords don't offer a significant (if any) improvement over the stock issue wrt Linn products and specifically the Ikemi. Surely different speakers, cdp or ICs should have much more impact I would think.Any other suggestions out there?
The last time I asked this question the concensus seemed to be room tuning, but I'm not sure exactly what that entails.
Tonyp54, I would at least try a good power cord and hear for yourself. Get it used here for less than 50% retail, and if you do not like it, sell it. I will not knock my fellow Audiogoners, but I trust very few pwople's ears in this world. You could also see what the power cord does for your amp. That might make a beg difference as well.