If you want a reliable spindle for less look for a RECON unit, a recon from a decent spindle brand will outlast and outperform any brand new Chinese offering.
5hp Italian Elte air cooled spindle run 5 days a week for over a decade with no worries- purchase cost as a recon was less than a grand (12month warranty). After a decade the thing wore out so we sent it back to Italy where Elte did a complete factory rebuild for 400 euro. This is CHEAP routing by any measure.
As far as VFD's go I'd recommend Taiwanese CUTES brand equipment.... we got 13 years reliable service before a refurb was required, cost for the refurb was less than 50% of the price for a new unit.
Air cooling isn't an issue if your spindle is properly engineered and carefully balanced during assembly- small hp Chinese spindles need water cooling... large hp European spindles don't. The difference between the two is simply quality.