There are two different "T 70" turbo's on Ebay.
The "XS Autochrome", or "XS Power" ones I know nothing about, but have read many accounts of how crappy they are. (Claims of glue, pot metal etc.)
Ok, Then there is the Master Power T70. This turbo is built in Brazil, and it made to specs that rival any turbo I've seen yet. And they are about 700.00 each by the time you pay all the fees, and shipping and the 599.00 for the turbo etc.
There are many MK4's and MK3's running this turbo with good results. Mid 500's easy on pump gas when tuned right and other supporting mods.
So, if a 3L engine can spin one up quite well, your 7+L motor should do just fine with two of them.
I'm also using the Ebay 50mm gate, and belive the quality is excellent for what you pay for the gate. (There is a 60mm gate now that is Vband mounted that I like even better, so you have more options.)
This is not a true "70" turbo either, more like a T66 with a slightly larger compressor wheel. (A T69.5mm if you will.) The P trim hot side has a .68 AR, so it's going to spool up pretty quick, but you lose some ultimate top end due to the smaller housing with the pretty large wheel. The shaft size is "small" but most P trims are that way anyway. No problems on any that I've researched.
If you want to learn more about Master Power, just do a quick search, they have a nice website that has photos of the plant, and people that work there. I like to think of my MP turbo as the "Tarus" of turbo's. All the quality of the Berretta, but 1/2 the price.