Their VPS 2 offer with 512MB Ram looks ok as a price point of view. Is there big performance difference between 256/512?

http://digitallinx.com/product_info.php?products_id=79

One of the concerns are that they don't have Plesk8 included to the offer.

I'm pretty sure they use LXAdmin as their control panel offer. My site runs fine on 256 through another VPS provider with similar credentials.

I have never heard about this company before. When was it launched into web hosting services market. It is possible that it is an entry-level company. You know, it's better to deal with time-tested companies, for example, glowhost.com or hostgator.com, they will do their best to meet your needs.