The Tour adds wifi connectivity. So you can access the streaming only content on the radio itself. I would get the Roady, because it's just a better radio. Less money and it boots up faster.
The cheapest solution would be to get yourself one of those cassette to aux adapter things. And that's what I would recommend. If you need bluetooth you can also pick up one of those aux to bluetooth adapter thingies.
Don't buy a cheap stereo to have installed. They're just crap, and tend to die because they're cheaply made.
A SiriusXM ready stereo usually doesn't include the actual XM tuner and antenna, you have to buy those separately. So consider that in your spending budget.
Have you guys met the 'casette aux adapter' ?
I have a friend who used to have this in his old ass car.
You can get an aux to cassette (example on Amazon - https://www.amazon.com/Arsvita-Audio-Cassette-Adapter-Auxillary/dp/B07N2KPTGW - they're available in some stores but you'd have to call around probably)
Then just plug it into your phone or if you have an old discman or something that'll work.