Yes I thought my 9515 (pictured below) had great SQ, even doing 143dB to music, daily driving. Loudest and best sub I have had the pleasure to hear. Of course I am no SQ guy but it made me happy in the pants...LOL

As for the diffence between the 99 and the 95, is mostly the cone material, and weight. The 99 has a stiffer, so less flex, and lighter cone making it more efficient. It is a kevlar cone instead of a non-pressed pulp cone.

 

15" Woofer Diameter
3" Voice Coil
4 Layer DVC
300 Oz Magnet
Synthentic Fiber blend Cone
1200W RMS Power Handling
2400W Music Power Handling
4800W Peak Power Handling
75mm Suspension Travel
33Hz Free Air Resonance
Qts 0.29
Qes 0.31
Qms 4.32
VAS 80 Liters
Le mH 0.9
Sensitivity 93dB
8 3/8" Mounting Depth
14" Cut out Diameter
47lbs Speaker Weight
51lbs Shipping Weight

The 9900s have the lighter kevlar cone. They also handle more power, are available in a quad configuration, and jump up in magnet size to a 320oz.

DD's recommended box designs are a very good mix of SPL and SQ.

I don't know if i'd recommend dropping the 9515 into a 2 cu ft box...

 

wow.. thank you. !!!