Pulled in four directions

Right now I am torn between four bikes. I’m not a great rider and I’m falling into the trap of having the N+1 syndrome with a 29 inch hard tail a 27.5 inch hard tail a 26 inch to 27.5 conversion that will become a gravel bike and now I want to add an inexpensive suspension bike to my bag. First bike is this $200 Diamondback Atroz 1 comp? seller says it has a new rock shop rear shock. I’m guessing a monarch. And it seems to be set up as a 1x based on the pictures. I have hydraulic brakes in the parts bin but would need to buy an air fork.

The second bike is a 2011 Cannondale RZ One Twenty–3 seller is asking $450. Good components all around and I found a company in the UK that makes an adapter for that one and a half inch head tube that adds one and a half degrees of slack. I have a 27.5 inch through axle wheel in my backyard and I think this would be a great candidate for a mullet. I’ve ever ridden one of those.

Number three I had never heard of until I saw it for sale. A Transition Covert for $500. 26 inch wheels full fox suspension front and rear a 67° head tube angle and it’s tapered. The seller does not know the model year but based on my Internet sleuthing, it looks like a 2009 or 2011. Pink bike wrote a glowing review of it

Last, and certainly not least, is this 2018 Giant Trance. 27.5 wheel The seller is asking for $600 but the listing it will hit a one year anniversary in July so the wife is out of town visiting relatives. I was thinking about making the 5 hour and offering him $500 for the bike.

Would love to hear everyone’s input.