Tivo Roamio or Roamio Pro + Mini & what to expect

It has been a while since I had a HD DVR from Cox.  
About a year ago, I dropped all the HD programming & quit paying for Advanced TV. 

My bill dropped from about $200 a month to about $125 a month. It was great, and we haven't been concerned w/HD.

But... Recently one of my 2 mainstay DVR's, a ReplayTV 5504, which I bought with a lifetime activation, back in 2004, has decided it no longer wants to tune channels.   I can record on one, and play on the non-tuning one, but it is a pain, as both only have a single tuner.

I'm wondering what to expect if I look a purchasing a Tivo Roamio/Roamio Pro + a Tivo Mini.  I understand the lifetime cost will be around $650, on top of the cost of the devices.  Keep in mind, my 2 ReplayTV's have lasted the better part of 10 years, with a lifetime activation cost of $350 each.  I'd say I got my money's worth out of the ReplayTV's.

So the cost of the Tivo's (low end) would be $200/$500 & $100/$150 or $950 - I'll probably use points for about $300 of it.
Then I'll need to get a CableCARD for the Roamio at $2 or $3 a month from Cox+ the service upgrade.

As far as channels go... I know I'll get all of the HD channels that the package includes, but what about the lower, non-HD, channels? The Roamio's aren't compatible with Analog cable, so will none of those be available? And if they aren't available as Analog, (I forget) but will there be a 1:1 for Digital to Analog channels?

Kind of on the fence... Really wish Cox just provided a Digital signal for all of the channels (now that I don't have any Analog TVs). And I could really care less about the movie channels/most of the "Advanced" content.

Any suggestions would be appreciated.