Gen2 comes in many varieties, ones that are really bad (cheap Russian tubes) and top of the line Photonis that rivals (and exceeds in some areas) Gen3. So yeah, Gen2 is fine
But in reality the Gen2 that is affordable and easily available is probably ones from ATN / Armasight and NGI. From what it seems NGI units are the best spec wise and a pricetag of $2k is great, considering you get a decent tube with great glass (PVS-14). In practical terms these medium spec Gen2 tubes lose to Gen3 in overcast starlight scenarios, but that can be fixed with extra illumination and then they show a great picture under any lightning levels.
Mounting NV behind optics non-magnifying optics is rarely done, it's much more usable hanging from your noggin. There are mounts that allow rapid mounting from head to rifle and vice versa.
My guess for the price of your ATN Patriot 2 is around $300 - $500.