Unsolvable Woofer Pumping (Phono only)

Little pieces of this puzzle keep coming in. I can’t afford and don’t have the equipment to drive a subwoofer...but would a more full range (i.e. floor standing) speaker be a better choice when I do decide to upgrade next?

When the subject is cost-effectiveness then:

Skip the filter, waste of money, won't improve the sound in the least. The clamp will, but only if you get a good one. 

Always in my experience the most cost effective upgrades are tweaks. By tweaks I mean attending to every single facet and component of the whole entire system. Things like Orange fuse, Cable Elevators, HFT, ECT, PHT will bring improvement far beyond anything you can get for the same money the usual way.

You could for example replace fuses in three components with SR Orange, add Cable Elevators, and a full compliment of HFT, ECT and PHT all for about $2k and no way no how will you ever find any turntable or cartridge or anything else for $2k that will come anywhere close. 

Then factor in that these are all "lifetime" in that they will all work wherever you go and whatever you buy forever. Its no contest. Nothing else even comes close.

Also power cords, interconnects, speaker cables, Cones, and Shelf. Same thing. You simply cannot find any component anywhere for say $500 more money that will do what a $500 power cord (or interconnect) (or speaker cable) will do for what you already have. Well, from Synergistic, I should hasten to add. Not that there aren't others this won't work with. I just happen to have 30 years experience that tells me with SR you can throw a dart. Everyone else you pays your money....

Note: not idle speculation- I have TRIED! Compared. Home auditioned. Put a $300 Synergistic Master Coupler on a phono stage, you won't get another phono stage that good (without the pc) until you're into it for three to five times as much. If even then.

My system is heavily tweaked out with all this and more. I've done demo's and removing even one or two of these people notice right away. Heaven forbid I should remove it all, let you hear what the same components sound like the way most people do. Shudder. Cue Brando: "The horror... the horror..."

Well you've certainly taken all the right steps to narrow it down, so good on you. With a lot of the most likely culprits eliminated we are down to only a very few good options left. One being, its perfectly normal flutter, you're just not used to seeing it. Most people with entry level tables have been raised on CD and don't know some amount of this is normal. Not being there we can't know if this is it or not.

Moving on.... your table has a felt mat and let me guess, you're not using a record clamp. So records lay kinda sorta flat. But not really. Problem being, anything other than absolutely flat gets amplified by the time it gets to your speakers by about a hundred thousand times. 

The solution is a record clamp. Not weight, clamp. Specifically, you want one that's cupped on the bottom, or has something like an O-ring going around the outside. Anything to create a space between the record label and the center of the clamp. Then you also want a thin washer, just barely thicker than your mat, that fits over the spindle. The idea being the clamp will press the record down forcing the edges into the platter making the record lay absolutely flat.

A good clamp used like this will almost always be a nice improvement, which since it will also work on future better tables makes it a fine investment no matter what. 

Since you say its noteworthy mostly when just treble this implies to me you don't really notice it with bass-heavy music, which in turn implies to me that whatever flutter you're seeing is no more than normal music level or less. Which to me means perfectly normal, you're just not used to seeing it. But whatever. Try a clamp and see.