so is it ok to get 2 different size subs to cover a wider spectrum of bass or get 2 matching subs?
To directly answer your question rather than blathering on about unrelated matters: Yes it's OK. The brand does not have to match nor the size. I have used subs as small as 6.5" with great results.
What you might consider is getting 3 or 4 subs which will go further in smoothing out the room response and when implemented well provides an astonishing result.
In a similar thread here: "Subwoofers ported or sealed" audiokinesis mentions his system and is worth looking into. Check out his SWARM.
My advice is to not be in a hurry, do your due diligence, read up on the concept of multi-subs as researched and advocated by dignitaries such as Geddes, Toole and Welti. They have all researched deep into the how, why and the spectacular results thereof. Their findings carry more weight than some posters here who do not have a clue.