Don,
You can use a phone to control your streamer if you don’t have an IPad. But, wow… not owning an iPad I can’t fathom that, we have about seven and most get hours of use a day. But that is a different story. Start with using your phone.
Getting a high end DAC as a starting place. Great idea. You can use your old transport, and for that matter you can use your MacBook as a streamer. With a really good DAC that will sound very good. It’s not going to compete with your analog rig, but it should sound very good. Lots of discussion here about using PCs because they can sound good and folks start claiming (without experiencing) you don’t need a streamer… after all there is a PC processor in it… until they experience one (or one in a good system), then jaw drop and they switch sides. I was reluctant at first (although not vocal) until I bought my first one… and that was the end of me ever using a PC.
On DACs… like analog… there are some detail scraping ones that will get you incredible detail an unnatural sound. You want a high end audio DAC that is natural and musical… if it is a high end one that is well reviewed as musical, it will have the detail. I really love my Audio Research Reference 9, very musical and natural. Used I am sure you can find at $5K