No less bass will go to the sub the lower you set the crossover. Basically what your doing is allowing more bass information go to your other speakers the lower you set the crossover. Think of it this way, by setting your crossover to 80hz your telling the reciever to turn on your sub when any frequency below 80Hz is sent. So your speakers play down to 80hz, when you set the crossover lower, then your speakers play down to 60hz before it is crossed over (or a better term handed over) to the sub.
Since bass is considered any note below 200Hz you could essentialy set it there, the problem is that bass becomes localized and you can tell where its coming from till it hits 100Hz, hence why THX recommends a rule of 80Hz across the board for a crossover (including large towers) the problem with this is that many speakers can easily achieve clean tight bass to frequencies down in the 30-40Hz (like the DT towers with built in subs)
Since you have a Pioneer with one universal crossover point, I would take the speaker that can handle the littlest bass and use that as a guide (in your case your rear channel speakers) take it's lowest rated frequency response, and go from there. But in your case 80Hz should be more than fine. it just means your center which can easily handle 60hz won't have to play from 60hz -80hz becxause you've told the reciever to hand off everything below 80hz to the sub, and that's just fine because SVS will easily play 80hz and below just fine, because that is what it was specifically designed to do. You'll be just fine with a 80hz setting.
One more thing to note is that mid range driver size is also important in determining what to properly set your crossover to, because it is the mid range that will have to carry the mid bass frequencies to the to the lower bass. So drivers from 5.25" to 6.5" and higher can easily get down to sub levels of 60Hz to 80hz, but say a mid range with 4.5" driver I would crossover at 100Hz - 120Hz, I have a pair of DT Mythos gems that have dual 3.5" now according to DT techs that means with dual drivers that it is basically a 7" woofer (I call serious Bullshyt on this one) because a 3.25" driver (no matter how many you have) can never reach the bass of a 7" driver. So for drivers of 3.25" I cross mine at 150Hz. hence why when you are considering speakers you should do some research and look for those frequency charts like in Sound and Vision and Home Theater magazines. It will tell you excatly what they tested with a semi staright line then the lower the frequency you'll see it suddenly drop like a rock, it's at that point where it dropped that the speaker couldnt handle any more bass and so dropped off. One of the reasons Bose are horrible speakers is their tiny 2" drivers can never reproduce anything that comes close to 200Hz and so it sends it's info to that bass module which is basically three 5" drivers and can only get down to 47hz (not exactly subwoofer territory) since many bookshelves can do that (not that they should).
Hence why when you read reviews and they show you each speaker and sub you basically want a straight line from 20Hz-20kHz, so they show the graph for the sub and where the sub drops off you want the speakers to meet up with the staright line of the sub.
Take this frequency response for the Hsu speaker system, the purple graph shows what the speaker can handle before it drops off at around 100hz, but that's okay because as we can see by the blue graph (subwoofer) it can get to 100hz pretty easy and if you follow a semi straight line the sub goes from 20Hz -100hz, then the speaker picks up where the sub left off and carries the stright line the rest of the way. There are going to be peaks and valleys but there are many factors for that (room it's in, placement of microphone and so on. There are only a handful of speakers that get a perfect ruler flat frequency response (Mackie 824 powermoniters are one). But what's the most important is how the speaker sounds to you the listener, just look for a speaker that can match with a sub and you'll be good.
Sorry so long.