Hi joji, I bought my China laser machine very recently, in fact it arrived a few days ago, so I know what it takes to do a good search for specs.
To start, if you want to do fine quality engraving, than lower wattage is better than higher wattage. And if you also want to cut 4-7 mm plywood, then I strongly advice to go for a quality (Reci or EFR) 80W laser. Reason: more powerful lasers have trouble working at low wattage and you need a low power for detailed engraving. 80W can go lower in working wattage than 100W (it still fires at a lower wattage). And don't go for another brand than Reci or EFR (with a 10000 hours tube life span).
Other things (in short):
- get a good chiller. Not the CW-3000 because that one doesn't chill. Get a CW-5000 or CW-5200, that will keep the temeprature of the cooling water easily at 18-20 degrees Celcius which is the best working temeprature for the laser tube. Especially important because Bahrein can be pretty hot.
- get several sized lenses. a 38mm will engrave with more detail than a larger one, but a larger one will cut better. Best is to get a 50 mm and a 72 mm IMO.
- Get spare lenses and a spare mirror set, they are cheap to buy with the machine
- Get nozzles and lens tubes for each lens type, they are vey cheap and it will make lens changing much more easier. Besides, different lens types need shorter or longer nozzles.
- Get other spares, like belts, stepper motor and motordriver, tube PSU.
- Consider buying a rotary attachment
- Don't get a spare tube, the tubes have a shelf-life and are losing some power, even when not used.
- I know Thunderlaser and the last 3 companies in your list, I also got quotations from them (for a 6090 machine), although Shenhui never responded to my questions. IMO Thunderlaser is overpriced, Bodor and G.Weike are solid companies with good Chinese machines. But do also conder Rayfine Technologies and Longtai, experienced users on other forums have good experience with these companies. In fact, there is one guy there who recently bought a 6040 laser machine from Rayfine.
Good luck with your decision-making process.