I have used the services of resellerzoom, they have oversold server, server load remains always high and site opens very slow. Moreover if your site start getting some traffic, they suspend it giving reason of server load.
You can use them if you have zero traffic sites, I don't recommend them for business sites.
I took the services trafficwala.com for SEO after reading reviews of their happy customers. Trafficwala did not disappointed me, they have very strong reputation for SEO and their work was according to that.
They were able to pull my site in top 10 in google, for which I was struggling since last many months and wasted money on some cheap companies.
Now I understand we should go only for companies with solid reputation. I recommend trafficwala to anyone looking for SEO.