Cannot buy Nitropad with Qubes preinstalled

As soon as i am choosing Qubes OS i receive the following Message:
This combination does not exist

We ship QubesOS only with 8 or 16 GB RAM and a SSD. Slower configurations don’t make sense IMO.

What about i5 or i7? Ist there a significant difference of Performance using qubes?

I will do most of My Work on a VPS via remote:
Nitropad With qubes -> connecting to my Windows VPS Workplace

So wont do much work directly on the nitropad and Just want to make Sure that i wont face any Performance issues while the nitropad ist connected to my VPS and displaying it.

I am Not Sure if i need to pay 250€ more to get the i7. What Specs do you recommend to make this Work without Speed Problems?

i5, 250 GB SSD and 8 GB, better 16 GB RAM should be sufficient.