Best way to spend my money

Many responders do not seem to realize that the OP is running 15 foot cables NOT between his TT and his phono stage (bad idea) but between his phono stage and linestage. That is perfectly OK, but since they are both balanced devices, it seems remiss not to be connecting them with a 15 foot pair of balanced, XLR terminated cables, as I mentioned before and as others have mentioned since. But spending a kilobuck on either the outboard Goldnote PS or a better cartridge are both also good ways to spend.  I would not buy an LOMC cartridge, if $1000 was my spending limit. I'd go MI or MM but definitely not HOMC.

@lewm is correct- unbalanced long runs picks up more noise, so it’s best to run balanced which greatly helps reduce/cancel such noise.  

Do the phono preamp power supply upgrade.  Since you list it I assume it's within your budget.  A 15 foot balanced cable doesn't have to cost much.  Pro music stores sell them by the boatload.

I am now able to visualise a Oak Table with a Table Top and possibly a H Frame design for the elevating of the Sub Supports and Sub Plinths. The H Frame is put together possibly as a Dowel Jointed Frame if a Modern Design or a more complex Joint if produced with an Historical Design.

An unknown footer type is in use sat upon the Table Top to support/separate a 4" Butchers Block, which also has an unknown Footer type in use that is sat upon it to support/separate a 50mm Plexiglass .

It is also assumed the TT’s Supplied Feet at sat upon the P’glass, to create a Space between the P'glass and Plinth, as well as assist with Levelling the TT..

I am now able to visualise a combined Weight of approx’ 8 Stone (50Kg) sat on top of a Oak Table Top in conjunction with the Support Frame used to function as the Sub Support for the TT’s 4 Tier Sub Plinth Assembly.
Nothing Strange in the above configurations the design is quite typical, even if materials and footers show differences to what others may have selected.

Removing the Focus on What is in use by the OP and commenting about all designs of this nature the following info will show not typically discussed info:

1, The Sub Support in use has to be very very rigid when substantial weight is to be mounted on it.
Some might suggest 8 Stone Sat Upon a Support is a medium weight.
The notion the Sub Support, especially the Framing to Elevate the Sub Support, looks quite well built is not sufficient, the Rigidity of the Sub Base is vital.

2, Weight when sat upon a Structure that is not rigid will be a cause for increased movement being created within the structure, resulting in a change / unpredictable changes Structures management of the local ambient energies present within the listening space.
A Structure that is moving creates additional unwanted energies to be transferred and a proportion will be travelling towards Parts being used where it is vital they are protected from such energies interfering with the function.  

3, All materials in use as a support are generally poor materials when it comes to Damping and Dissipation, even though the purpose for them to be a Structural Material is fine as a choice if strength is all that is being considered.

4, Intrinsic Properties belonging to materials can be Objectively Assessed using methodologies for measuring  materials. Commonly Selected Woods are showing very similar data, - Oak @ 0.102 - Butchers Block @ 0.1 - MDF - 0.017 - Metals also are similar - Steel @ 0.008 - Chemical Based Substances share similar as well - Plexiglass @ 0.07
The Data reveals one important trait attached to these material types.
Each is not efficient at being able to stop Amplitude, the energies transferred into them will pass through with little resistance and be able to migrate into other Materials used Locally.

5, In the Sub Support and Sub Plinths, energies will travel through to the Plinth of the TT. 
The TT's Plinth Materials as individual materials are the least effective at reducing Amplitude.

6, The Stylus is in contact with the Groove with the design for it to extract a facsimile of the Data embedded within the Modulation in the Groove and send this on for conversion to become a Electrical Signal to be Amplified.
Any energy created and being passed to the Stylus that is not from the Groove Modulation, is not belonging to the embedded data within the Groove.
Energy passed that is not energy created as an embedded data is an energy that is having the effect of being an adulteration of the energy from embedded data.
Energy that is an adulteration of embedded Data energy is sent through the Cantilever for conversion to a electrical signal, that as a signal is to undergo various stages of Amplification/ Increased Gain.

7,The Signal will become and End Sound at the time it has exited the Xover as a divided Signal to create different frequencies within the End Sound Produced. 

With the above in mind and rigidity being of the utmost importance to give certain material types their most effective environment to function efficiently in. 
Imagine what is the potential if the actual supporting structure, such as the Rooms Floor is not rigid.

Taming the environment the Analogue Source is set up in, to create an Interface where the Stylus is protected from receiving unwanted energies, is a life long interest and not able to be addressed with immediacy. much learning is to be had, if this is an area of an audio interest that has appeal.

I have stated in the past, " On the Gon,  there are Analogue Source Users who have kept an Open Mind about such a subject of Isolation/Separation, but were at a place where thought was suggesting little else was achievable.
I have read reports where simplistic changes at a later time have been Jaw Dropping Good as the Outcome. 
One very well recollected report made by a well respected Gon Member, was about how the Analogue Source noticeably tidied up when they made an inroad to rigid up the Sub Support for the TT.
Note: This Gon Members TT is also produced using as multi tiers one of the most attractive materials in use today in audio for the Intrinsic Properties for Damping/Dissipation.

My basic Take as a result of experiences had, is Analogue Source / CD Source are able to be very very impressive and wanted to be used regularly.
When the Signal Sent from the Stylus is seemingly as unadulterated as possible that can be achieved using a certain level of knowledge to achieve this. The reasonably affordable TT Set Up will be able to make a very very good impression. Parity of performance is available from the TT to many many CD Sources, to some extent the CD Source being substantially more expensive than the TT used.