You rightAdventurer is pretty rare RV so you will likely pay premium just suck it up and get out there and start enjoying it. With inflation your cash worth less everyday.
I know this is an old thread, but the two units he is looking for are a really unique layout for families.To my knowledge there no rv or expedition trucks out there with seating for 8. You are looking into bus size! Aside from the secure and certified belted seating, where do you set up 8 beds and still have room for a bathroom, kitchen and room to store all your gear? Not even talking about sporting gear like bikes etc...
I would seriously consider two vehicles. These can be much smaller and will get you to much more places. In that case your $150,000 may be a bit tight.
Good luck!