Speaking to the Sound Dynamics 300 ti's, the ti signifies the titanium dome tweeter. SD was a division of API, Audio Products International, which also produced Mirage, Energy, and Athena. Mirage also uses a cloth-damped titanium dome tweeter and has that same relaxed yet detailed treble.
I recommended the 300 ti to several audio newbies back when SD was still in production, and everybody who got them was ecstatic at their performance vs. the price. But that was back in 1996-98. Still a great speaker if you can find it, but if you can't the currently available Mirages will definitely do the job while having broader dispersion and lower box resonance owing to the curvilnear enclosures.