I had a 605, way back. The only difference IIRC between the 705 is that the 705 connects to sensors. Be warned - the UI on them is absolutely horrendous. I found it very difficult to get on with -the difference in use compared with today's units is like 2000s Linux compared to 2019 Mac OS.
looking more around £100 for a second hand unit, rather than a new one
just put in some bids on a 705, might be a stopgap or I might like it...