I would just go straight for the 500. I had the 200, which is a great amp, but was always wishing I'd spent just a little bit more to get the 500. At some larger gigs i had to really push it to keep up with the rest of the band and i didn't feel comfortable cranking it that much and was worried about blowing my 115 Rumble speaker. Eventually, i added a 410 which, as you correctly state, allowed me to gain the full 200watts, instead of the diminished 140watts you get when using one cab.
Even so, i would still have got the 500 if i could have my time again.
There is a school of thought that says you should get a smaller combo amp for rehearsing/bedroom use. That's fine if you want to spend the cash and have room in your home to keep 2 rigs but i would say that, if you got the 500 plus one cab (115 or 410), it would be small enough and certainly light enough to use at home, no problem. As you say, it's got a volume knob (and headphone socket) so use it! My 15 year old son has inherited my 200 amp and 115 cab (i had to sell the 410) and he is perfectly happy using it at home for practice or taking it to gigs with his band. Hope this helps.
This definitely helps as if you were reading my current mind.
I was T H I S close to pulling the trigger on a Rumble 200. LOL
My mindset went this way as I began my Rumble plans: Ok, the Rumble 40 sounded really good but it simply is not and will not be enough so if you're going to get the 40 just get the 100.
Ok, the 100 is $100 more and really is but what maybe a few dbs more so you still lack the power and headroom and you cannot add a cab to the 100 so go to the 200.
Ok, the 200 is PERFECT. I love a 15", it has decent power alone BUT you now have the ability to add a cab and get the full 200 watts and it's only $150 more than the 100 so you're good to go.
Ok, let's say I get the 200 and go ahead and get a 410. You know damned good and well you are still gonna want that 500 only now you will have to sell your 200 used which means instead of spending an extra $150 NOW to just get the 500 you will have to spend an extra $250 later. (this is because selling the used 200 means taking a $100 loss which ends up being sort of a "rental fee" for the time you used it before graduating to the 500. Never again will you be able to move all the way up from the 200 to the 500 for just $150 more)
You know you want the damned thing. It has a headphone jack and volume knob. You can add a cab when you truly need/want more at some point down the line.
Now, in my perfect little dream world where my wife says, "Oh please honey spend all you want on everything for bass guitar because I love you and you deserve it and well, I don't need a vacation with a bass God like you around the house!", I would get a Rumble 500, a 410 and a Rumble 40. (Man oh man did I LOVE that Rumble 40.)
I do not live in that perfect dream world so it's either get a little better amp and then GAS all over wanting more which will end up costing way more in the long run or biting the proverbial bullet and going 500 now.
I have already told my wife how light it is and she was not impressed and even tried to play her several YouTube review videos and well, so far she seems happy enough with my Hartke but she won't have a problem if I get ONE amp.
Her fear is I will fill this place as I want to replace my drum kit and let's say she doesn't exactly share my belief that covering every wall in soundproofing material looks way cooler than anything she can pick up at Kirkland's.
So, it appears I will be joining the Rumble club and will end up going with the 500 because it just makes sense.
Hey, I can at least tell my wife how it makes way more sense than say the Orange 100 would have given the bang for the proverbial buck along with that amazing Rumble tone.
