Network speeds by device

I plan on purchasing a Tmobile phone, most likely used on ebay. The main reason I want to get the phone is to use it as a mobile internet provider via tethering. I have narrowed it down to buying an Android phone on Tmobile. I do not want to buy an expensive phone such as the s3 if my connection speed while tethering isn't even going to be much of a difference than any other 3G phone- I'm not interested in getting an LTE phone right now. So my question is, which phone would be the best value for using via tethering, does it matter which phone I get that supports HSDPA/3g? (from what I understand people call HSDPA 3.5g/4g but it is actually truly just 3g) For instance, if I get a deal on a myTouch for <$80 would it go pretty much just as fast as the s3 for >$300 would go while tethering? Also wondering, what type of phone would be the best value for tethering on Tmobile hspa while getting a very fast speed? Thanks

edit: I think I've narrowed it down to wanting a phone that can handle DC-HSPA+ but which phones offer this? Is there an easier way to find all the phones that support this other than googling them individually?

 

There is no unlimited plan for the mobile hotspot. I usually use about 50gb+ a month.

 

I'm not even worried about battery life, I just hook my phone up via USB cable to my laptop and it never runs outta battery and I tether the data over the usb cable, no need to actually use wifi or pay extra money to tmobile..