Straight pipe means no resonators, and no mufflers, just pipes from the cat, which is pretty loud.I say try out resonator delete and an x pipe first, it will be cheaper, then if you dont like it, just install those borlas with the x-pipe you'll have on.
If you want a louder exhaust, I doubt you'll find it with borla. I wasn't happy with the volume when I had them. I went from stock mufflers, to borla, to flowmasters, to magnaflows, and now bassani. Out of the 4, bassani wins, no doubt.
Borla is very close to the magnaflow sound, both sound european but I from I remember, magnaflows were a little louder. Borla were the first aftermarket mufflers I had.The sound was nice, european, but they were not very loud. I took of the resonators with the borla mufflers and the stock h-pipe the ls comes with. I was not satisfied with the sound so I went with flowmasters after just 2 months to get more volume. At first I only had the flowmaster mufflers installed, but it was way too loud without resonators, so resonators went back on. It sounded loud enough in terms of volume with resonators, but the sound quality was alright. Then I went with new 2.5'' pipes from the cats,no resonators, x-pipe and magnaflows installed. The sound itself was very nice, but the volume was not what I wanted. The thing I didn't like about the magnaflows, it seems that they wouldn't get louder after about 3000k-3500k, which sucked when I got on it and wanted to hear the exhaust. It sounded like it just stayed the same after 3500k and on. A few months ago I bought bassani mufflers and just swapped out the magnaflows for the bassani. Bassani has like a european with a slight muscle car sound and good volume. I am very happy with these mufflers. They get louder and louder through the whole rpm band, which is how a muffler should sound.
If you want to be different, try out corsa mufflers, haven't seen an ls with those.