Of the two, I'd go with option 1. I wouldn't place sub-woofers behind your L&R main speakers especially with only 10" of space. This could impede the LFE's eminating from the two subs. Placing one sub 4' out in front of one the two main speakers would be the better location if that's all you have plus 10' away from the listening position is a good distance. I use two B&W ASW-610s for my rectangular room with a pair of B&W 683s as my mains. Both subs are apart from each and they balance the LFEs beautifully. If you could find space in your room for this approach, that would be best IMO. I'd consider using a B&W subwoofer (DB1 for example) which is part of the 800 series. If you don't need that much output, the ASW610XP may also be a great choice.