Have you taken a look at Lagoa? I think it would fit your bill. It’s cheap ($50 a month, with a free version as well), and does great interior/exterior shots. One of the nice things about it is that you can run multiple simultaneous renders at the same time with no slowdown on your local hardware, since all the rendering is done offsite.
If you can afford to fork out the money for modo, it’s an excellent piece of software (I still use it for modeling and occasionally rendering, it’s a got a great ray-tracing platform).
I’m suggesting Lagoa because I honestly think it might solve your issue, and I’d like to know what you think as a practicing designer - why or why you wouldn’t choose it for your next platform.
Here’s a blog post I did with a bunch of archviz renderings using Lagoa, if you’d like to see some examples;
http://home.lagoa.com/2014/02/lighting-for-architectural-vizualization/