Personally, I have never heard a recirculated HKS...but:
I did a lot of checking up on the HKS recirculation, and from what I've read, recirculating it makes it sound like a little louder 2g stock BOV. It definitely won't sound like all the little HKS clips and videos you've been watching/listening to that are on Supras and WRXs, guarenteed.
What makes the HKS sound so unique is the little "fin" inserts while venting to atmosphere. Since you can't have those inserts on while recirculating...all you have is a pretty expensive unobstructed valve letting air by, which will make a woosh sound...not that "squueee" sound you're probably looking for. To get that infamous HKS sound on a DSM, you'll need to get a MAFT (way too much time and money if you're just looking for sound).
I had this same dilema a couple months back, and after quite a bit of research and looking at pricing, I decided to go with the GReddy line of BOVs, which sound great even when recirculated, and are a little less expensive.
I'm not trying to discourage you from getting the HKS BOV, because it is a very well designed product, but if you are just looking for that HKS noise...you'll be disappointed having it recirculated. If you want just a woosh, then you'll have to get more info from someone that has theirs recirculated
