So… I’m 5 weeks in flower and I have yet to purchase a fan & filter. My house stinks! Which is fine but I’m thinking I really should get a filter. Does anyone recommend AC Infinity 4” fan? Or should I really go with a 6”? I only have a small tent, it’s 32x32x64 and I’m probably only going to have one plant at a time. I’m trying not to spend too much money as I’m moving soon and need to save money.
I would go with a 6" The 4" fans I have had were pretty weak. I have 2 infinity fans. I would take a standard fan over these any day. These Infinity’s I have are louder and flow less air than some thing like my vivosun 6" fans. They work good. Just a step below in my O2. There are a lot in here that really like them though. But I would look at a 6" either way 
Definitely 6" fans. You can get two of them (one intake, one exhaust) for about 15 bucks a piece.
I purchased 4" fans for my 2x4x60" tent and returned them for 6"
I concur, get the 6"
Also, do waste your money on the AC infinity filter. The vivosun filters are much better for smell and cheaper
4” would work but 6” would be better