HY-100 wasn't done for depth considerations but rather for the operating environment. The original 688 was never intended for under ice operations and as such had to be modified to replace the 637 class. The modification removed fairwater planes and brought retractable bow planes into the mix and, most importantly, reinforced the sail and modified the mast and antennas with an 'under ice' mode. (again, all open source info readily available).
Virginia and Seawolf are two very different creatures 'under the hood'. SSN 774 class were designed to not be refueled for the life of the hull. SSN 21 class was designed for high output and to be refueled, so depending on EFPH over time, ten to fifteen years between refuels. So the 774s basically came with a "governor" on the engine to keep reactor life where it was intended to be...21s were cold war monsters designed to shoot 8 weapons at once, carry over 42 weapons in the torpedo room (actually two HUGE rooms to take out a whole Russian battle group on her own) and to get places FAST. The 774s were not designed with the cold war mission in mind but were the 'jack of all trades'. That's why there's also a lockout chamber in upper level for SOF personnel (and that is not taking into account the DDS capability if so equipped). Her sail is also 'modular' allowing for installation of special purpose masts if ever needed. 774s are also VERY cramped, one of the upper level berthings has passageways about 20-24 inches wide (even the racks were harder to get into). Seawolfs are wider (44 foot beam) and more 'crew' friendly.
The 21 class removed the vertical launch tubes due to issues with maintenance, 774 reintroduced those tubes (block III will move to 2 large SSGN like tubes).
Where they are similar is use of TB 29, WAA, Spherical Array (until block III 774 which will introduce LAB or large aperture bow array) and the combat system/sonar/ES fit (BYG-1/BQQ-10 and BLQ-10).
With respect to noise suppression, they also differ. They also differ drastically from the 688/688i as well.
There are good sources of information out there, but I would shy away from 'wikipedia'. I would lean towards Jane's Fighting Ships for this type of data...the book is expensive ( roughly $1000 ), but it's a good source that is constantly updated.
As for how good surface towed arrays and SONAR sensors are...
http://www.allamericanblogger.com/12773/chinese-sub-surprises-u-s-aircraft-carrier-battle-group/
http://www.washingtontimes.com/news/2006/nov/13/20061113-121539-3317r/?page=all
If you read those articles, it should shed some light based on real world info...so between those and the Jane's fighting ships, a new guesstimate could be made on detection radius of the SQR-19 TACTAS for example. Add to that US crews have high op-tempos (time at sea) and are constantly graded on their proficiency (so boats at sea are pretty well trained), you should assume that the Virginia is a hole in the water...so are the 726's and 21's. The 688/688i are still pretty good and can hold their own with a good crew.
Also, why are there harpoons on the US fast boats?