You have so many questions, I’m not entirely sure what you really want answered here. Though, it seems you are looking for a good preamp. In general op amp technology has really advanced with opamps that have come out in the last 10 years. However, usage of op amps versus discrete or Class A is entirely dependent on your application and what source you have. If you have a very laid back analog or tube source (such as a tube DAC), then a high-speed accurate bipolar preamp may be a good match. Or maybe go with a passive preamp with a higher impedance attenuator (like 100k ohms).
If you have a very solid-state DAC source that only uses op amps, then you probably want to have some sort of Class A preamp. But be aware of what you are using as some op amp sources are engineered to sound warm (like NAD or Adcom or even Emotiva XDA dacs). Many use the OPA2134 FET based op amp for this purpose (the lm49720 / lm4562 op amp is also used somewhat like this). In my opinion OPA2134 is a really poor op amp that smears the sound to make it warm sounding and you also lose resolution.
You have purchased an Aragon 8008BB, which is a very nice amplifier. It is biased high into Class A (the initial 26 watts if I remember right). Also, this was designed by D’Agostino and he likes the warm/rich FET type of sonic signature. I have heard this amp and it is very warm and rich sounding. However, as a byproduct of the warm signature with the Class A bias, it is definitely on the warm/slow side and you can sense a slight smearing of the sound. Nothing wrong with this -- it’s part of its sonic signature.
So, based on that, I would look for a very fast accurate bipolar-based preamp, such as the Rowland Capri you mentioned. The OPA1632 is a bipolar opamp with very good specs. It is going to be very clean and very fast. I would avoid Class A or tube preamps with your Aragon because there is going to be too much smoothing of the waveforms going through several Class A circuits and you will have a slower sound and the high frequencies may start to roll off. But if that’s what you want, then great.
I remember the older B&K stuff being very warm. It is actually too warm for me. You might want to look for a transparent/clean type of preamp. Cambridge Audio Azure 840E-B? Or the Wyred 4 Sound STP-SE?
The Freya uses a JFET solid-state stage which will add a warm/rich signature.