Yeah the fender rumble 500 is like 35lbs or something and a 1x15 ext cab weighing about the same. So you can have a 35lb amp for practice and small gigs with another 35lb box for the big gigs. All at or under budget brand new with warranties and such. 500 watts, 210 115 and a horn... boom
And if you keep your current rumble your practice amp and main rig will feel the same.
The ampeg 410 cab is 75 lbs by itself, plus the amp, god forbid there's stairs... And even used, head + cab makes your whole budget or more. And if it breaks there's no warranty.
This^. Also, if you would want to sell the Rumble (for whatever reason), I would expect it would sell easier, faster than a dated and unwieldy Ampeg. Whatever you decide, try to find one used and in good condition. Be patient.