Since (for me, as a MTL vaper) the GS tank is the "perfect" topper...and since TC heads are available for the GS tank...I, too, have been looking for an "inexpensive" TC Mod.
I've got it narrowed down to the iPV D2 and the TC40W istick.
They're very close in size and somewhat close in price.
The TC40W has a 2600mAh built-in battery while the iPV D2 uses a replaceable 18650.
Was it the replaceable 18650 that led you to chose the iPV D2...or was it something else???
I'd go with the D2, I don't love the istick 40 so far. The temp control seems to struggle. I have had a lot of trouble with fluctuating coil ohms reading. I spend a lot of time adjusting the temp to match the new reading. My evic VT works much better I set it and forget it, I lock the ohms and it never changes.
I just ordered an IPV4s to check out their temp control. I have heard good things and the price is good right now.