Well you've got quite a choice of DAC / pre-amps within your budget. Seems like you'd be able to get away with a USB input only initially. But now is the time to consider the inputs you might like for the future - and even from the off, one with optical and / or coaxial would allow you to connect the digital output of an existing CD player, for a potential sonic improvement.
Having tried several DACs ranging from £100 to around £600, I've found (and I'm not alone) that the (sound) differences are subtle to say the least - although I've heard it said that you need to spend at least £1000 (But there's more chance of me being the first man to set foot on Mars than ever spending £1000 on a DAC).
(I currently use a couple that cost me around £100 each, one for headphones, one for hi-fi amp).
As for reliability, I understand your concern but I wouldn't be unduly worried - I think there have been significantly fewer reports of failed DACs than most other products (though it's fair to say that for most, it might be too early to judge longevity - I work in decades where others are happy with years).
With your sort of money spare (and it would have to be spare) I might consider the CA 200M you mentioned. In fixed output mode, it could connect to a line input on your Pioneer amp.
Thanks a lot for your input on this. I have read some things related that the improvement in sound quality on a system, would not be so noticed, replacing a DAC, but more, replacing/upgrading the speakers or the amp, and they really are the older ones. But as I told, I need to go step by step.
I am also more for the decades on the longevity side. The Pioneer I have, I can't complain very much about it. The turntable, the rubber belt sort of desintegrated, but it was there for over 20 years, without any use. And the tape decks, it seems, they dont' have more enough power, to roll/turn on. Perhaps they are full of rust or something. But the amp, the speakers and the receiver, they still work. And they are over 30 years old. I lost the count of how many times I have played U2's Achtung Baby, when it was released back on 1991, on my turn table.
Nowadays, I don't have great expectations over electronic devices. If they last for a decade, like a Toshiba LED TV that I have, I will be a very happy man.
Thanks again, for your time and advice.