Ya... I call them Arankal, whoopty do.
How strong do you think that the arankal should really be? When Hitsuguya said that it would take only 10 Arankal to destroy all of Soul Society, how could he have known that Espada existed? If there are 10 espada, then what the hell do the others need to be around for? All the people who came from Soul Society had limiters that took off roughly 80% of their power, which means that they were fighting the normal Arankal with about 20% of their power. After taking the limits off, Hitsuguya and them pwned the Arankal and didn't even give them a chance to attack. That means the Arankal were beaten when the higher-ranking shinigami were using full power and that they (the arankal) were only at about 50-70% of the shinigamis' strength.
Back to the question:: How the hell will Arankal whipe Soul Society off the spiritual plane if they are that weak? When he was giving Ichigo the explanation for the classification of hollows, Hitsuguya wouldn't have known jack shit about the classification system that Aizen made for his arankal. If that's the case, how would any random group of 10 Arankal just walk into and wreak havoc on soul society if they are so insanely weak compared to one of the weaker 13 captains (Hitsuguya). Seriously... he's got to be one of the weakest captains in Soul Society, so weak that Unohana can prolly obliterate him witih Bakuda. The weakest captain in Soul Society managed to kill off a really strong arankal without putting in that much effort after breaking his limit, a limit that wouldn't be present if they were all fighting in SS. And if all the Espada, including Grimjaw, were to attack SS in their group, wouldn't they just get pwned by people of Yamamoto's and Zaraki's power? Zaraki pretty much beat out two captains of Soul Society (we all know he would've killed Komamura), and Yama-jii can't exactly be laughed at either. Then, there are Ukitake and Shunsui, two people who can stand up to Yama. Fighting together, they can probably take anyone. Next, take into account the people not in Soul Society, Isshin, Urahara, and Yoruichi. These three are all at the captain level or higher, so they would definetly have to make appearances in Soul Society to help get it out of the shithole it'd be in if attacked directly. So, that would be at least 16 captain level shinigami (I included Renji and the people he taught, none of whom broke their limits to kill the Arankal) against 10 people who can go even against Ichigo's Inner Hollow (not sure if he's Vizard or not...).
How would Arankal be able to destroy soul society if they are so insanely weak in comparison to shinigami? The only way that they'd stand a snowflake's chance in hell would be to have their own versions of Ban Kai, which will probably happen if Aizen decides to open a portal from Hueco Mundo's deepest regions into Seireitei with his espada.
I think that Aizen probably redoes a few of them with a modified form of Hou Gyoku to give them the refined abilities of shinigami... That's the only way he'd be able to win without doing any real work himself, at least.