The PSB speakers are very warm and full in the midrange, but they are warm and soft sounding and will not have the clarity of the Snell (this is due to the polypropylene drivers used for midrange and bass). Don’t get me wrong, they are very pleasant speakers to listen to, but they may not have the clarity and resolution you are looking for.
If you are looking for clarity, maybe the Monitor Audio Silver or Gold series could be good. They are very crisp and clean sounding. The midrange is very strong and clean. They can have a tendency to sound a little bit bright, but I think they are going to be closer sounding to the Snell J. The Snell J was a very clear sounding speaker, but it is a bit recessed in the midrange body. The Monitor Audio will have a fuller and stronger midrange. The Monitor Audio is also a more exacting speaker, which means it is not as forgiving as the Snells. In other words, it can began to reveal flaws in your electronics and cabling. The Yamaha is not the best electronics, but I think it is more natural sounding when compared to other receivers. The Monitor Audio Gold 200 floorstanders are $2249 each, which is more than PSB T2 ($1749 each). Monitor Audio Silvers are very affordable, or you could look for a used Gold.
For the Yamaha receiver, one of the things I have found on these is that it is better to set the speaker impedance to “6 ohms” in the ADVANCED SETUP menu. Read the documentation on this. Speakers today can be listed as 8 ohms, but many have impedance curves that can drop down to even 3-4 ohms.
The Yamaha V679 receiver has a hard-wired power cord, so you cannot upgrade it. However, I have found that a fuse upgrade can improve the solidness of the sound significantly. It really depends on what you’re looking for. I had a V663 receiver that used 2 small sized 10A fuses. I found that a combination of one Furutech and one Hi-Fi Tuning Supreme worked best in this model. If you chose PSB speakers, I might recommend doing two Hi-Fi Tuning Supreme so that the attack and detail was boosted as much as possible. If you chose Monitor Audio speakers, then two Furutech fuses might work out best because they are more laid back sounding than the silver Hi-Fi Tuning.
Finally, speaker wire. My default recommendation is look for Audioquest speaker wire. My minimum recommended is always Type 8, but you can look for Rocket 44 or Rocket 88. Please make sure you have banana plugs on one side for the receiver (nothing else will work). I would keep away from the silver-plated banana plugs. Audio Advisor has great prices on their “No Frills” versions of Type 8 / Rocket 44 / Rocket 88. Or you can look for used, which can include things like the Granite / Bedrock / Slate series.