There are 2 issues here - the sound and the convenience. Let's start with sound.
Is the Denon the DP-S1 - a landmark product? If I remember correctly, it is a transport. I believe that the Theta you are referring to is actually a DAC + preamp. The DAC already supports 24/192 inputs. So, I believe you have a transport plus a DAC in the system. Replacing a DAC can make a dramatic change to the sound of a system. The PWD is a fine product, but it may have a significantly different sound. You need to be careful with that.
A NAS based system with a GUI is a very flexible system. But it also means that someone needs to rip the files, which is not a hard task for common CDs (although it can be time consuming), but can be a challege for more off-beat CDs and for many classical CDs. Is that a task your father wants to take on? And, what type of music does he listen to? Is there a good set of high rez files that he would be interested in?
How about going at this slowly by setting up a trial system by just replacing the transport. If he has a laptop he can use that as a front end. If not, a $300 netbook is a decent start. Then he needs a USB to SPDIF converter so you can feed the Theta. Something like the m2tech Hi-face is only $125. Add a software player (I like J River Media Center) and you have a trial front end for not much money. then he can rip some CDs and he is off and running. If you can set up a trial system like that, he could get an idea if that type of front end makes sense for him. This may well not be the final front end, but it is a way to test the process for not much money, especially if he has an existing PC he can use.
Getting a PC type front end set up is relatively easy. But it is more than just hooking things up. You have to be very careful with the sound and with the total ease of use, including ripping.
My advise - take it slow.
Is the Denon the DP-S1 - a landmark product? If I remember correctly, it is a transport. I believe that the Theta you are referring to is actually a DAC + preamp. The DAC already supports 24/192 inputs. So, I believe you have a transport plus a DAC in the system. Replacing a DAC can make a dramatic change to the sound of a system. The PWD is a fine product, but it may have a significantly different sound. You need to be careful with that.
A NAS based system with a GUI is a very flexible system. But it also means that someone needs to rip the files, which is not a hard task for common CDs (although it can be time consuming), but can be a challege for more off-beat CDs and for many classical CDs. Is that a task your father wants to take on? And, what type of music does he listen to? Is there a good set of high rez files that he would be interested in?
How about going at this slowly by setting up a trial system by just replacing the transport. If he has a laptop he can use that as a front end. If not, a $300 netbook is a decent start. Then he needs a USB to SPDIF converter so you can feed the Theta. Something like the m2tech Hi-face is only $125. Add a software player (I like J River Media Center) and you have a trial front end for not much money. then he can rip some CDs and he is off and running. If you can set up a trial system like that, he could get an idea if that type of front end makes sense for him. This may well not be the final front end, but it is a way to test the process for not much money, especially if he has an existing PC he can use.
Getting a PC type front end set up is relatively easy. But it is more than just hooking things up. You have to be very careful with the sound and with the total ease of use, including ripping.
My advise - take it slow.