The G0705 has a round column. That is pretty much a no-no.
The G0704 is only 290 lbs shipping weight. That includes the base and the shipping box/crate. I think that is way too small.
The G0619 is a machine that has been converted many times. It is also the same machine Syil used for the SX3 CNC they used to sell (discontinued). You may be able to find a used Syil CNC conversion in good working order for around $3500 (some Syil conversions go up to 3000 RPM, as opposed to the native 1750 -- makes a big difference) or you may find a conversion kit for the Grizzly version, or you may find people that converted it before.
If the G0705 represents your upper budget you should look into the G0619.
There may be others to consider, but I'm not up to date on these machines anymore.