Won't be less expensive, but at least your money will go in the right parts.
TDC: wobbly, useless, needs replaced with a Hadron anyway.
Barrel: completely unnecessary, stock TM barrel is perfectly fine, so is the STTI
Hop rubber: they come FILTHY from the factory, though this does not really affect performance. It's €8 anyway for a new one.
Metal slide: useless, expensive and adds a bit of, again, unnecessary weight.
All the springs and moving parts on the TM are infinitely better, smoother operation and will last 10x longer. The springs on my SSX23 fucked themselves after less than a year.
That doesn't work unless fully assembled, and at that point it's longer and wider than the TM.
Back to the OP:
Get a TM Mk23, leave it alone for now as it's perfectly useable out of the box with the exception of the hop up adjustment being a tad annoying.
At a later date get a Hadron TDC (it's more quality of life than anything else) and maybe a new hop rubber.