Magnepan SMG or MMG can be had for that price. Your Onkyo can handle a 4 ohm load the speakers sound great. Sky is the limit with them and that is what I started with. I have since evolved to Magnepan 4a and 3a in another room. A newer receiver will not have the power to drive them. Old receivers or power amps are the way to go.
These type of speakers are not heavy base speakers. If you like rap, metal or hard rock look to something else. If you want awesome vocals, highs, mids and base sounds that actually sound like an instrument and not a big boom. Definitely look real hard at Magnepan.
You are loading that Onkyo at its' max, so if it is not working well, you will need a better amp and it will not last long on a 4 ohm load. Modern receivers often just can't handle this type of load. If it is working properly, these will sound great.