Swapping Kt88 tubes on muzishare x7 for Kt150

Your KT88s should give fine bass.  I don't think your problem is your amp.

I'm using the Wharfdale denton 85 bookshelf speakers but i feel like the bass be deeper on this pair

The dynamic range can go as deeps as 45hz. I used to have a focal pair that went as low as 55hz and the bass was very deep

hvuck OP

"The dynamic range can go as deeps as 45hz.

You are confused, misinformed, or disoriented dynamic range is not measured in hZ but in dB.

The answer is NO. You want deeper bass correct? Reinforce the bass, move the monitors closer to the back wall. If they are on stands, beard the stands the width of the speaker from the base to the floor with just card board and watch how much the bass improves. You can make it wider or narrower but the BASS will improve. It may not go deeper but to tell the truth it's a bad idea anyway.

60-80hz is a better cut off and then the timing isn't so screwed up. Blending a sub is really easy with that type too.  LOL Sit on the sub.. The fact of a sub being a lot closer to the seated position and decoupled, might really surprise you how good it can be without backing the screws out of the sheetrock or the neighbors for that matter. 

Placement is the key first for more of what you already have. If the speaker can't reach that deep, you have to add it, simple.