New Spindle

[JAZZCNC]

My suggestion is don't mess about with likes of Kress etc which are air cooled and buy either 1.5Kw or 2.2Kw WC spindle.
Personally I'd buy the 2.2Kw because it gives larger cutter range usng ER20 collets 1-13mm were the 1.5Kw use's ER11 collets 1-8mm which is more restricting.
The 2.2Kw will cut aluminium all day long no problem and engrave to very good standard. ( See here for the level of detail )
VIDEO0021.3gp - YouTube

The advantage of water cooled is the duty cycle is 100% so basicly you can leave it running for days if needed, which I have done often.
Air cooled spindle often have duty cycles between 50-80% with only the better and expansive ones being any good for prolonged running, 8hrs +.
They are also very loud compared to WC spindles, I can stand next to mine while it's light cutting, such as engraving and talk on the phone.

Don't need any fancy plumbing either like you see some doing, just a plane submersible fish tank type pump dropped into a large-ish sealable container 20-25ltr of distilled water/anti freeze mix. The only requirement of the pump is it must have a head height capability higher than your Z axis goes. (most do at at about 2-3mtr)

It's No contest IMO unless you need really low speeds (lower than 5K rpm) for say cutting metal has nothing else off the shelf can touch them for power and money.
If you need low rpm speeds then It's completely different ballgame which won't get into now unless you do.?