I have a Skylink SC-1000 system. It is a good quality wireless security system. The cosmetic design is somewhat inferior to competitor products but the functionality is better than comparable products in the market with similar price range. The quality control can be improved. But to be fair, this is the same for other brands of wireless security system in the market. The manufacturers are under pressure to reduce price in order to penetrate the market.
As some reviewers in Amazon.com commented, there are some features that are desired for future improvement. The SC-1000 has been in the market for some time. Customers may want more features in the product as technology advances. But in the meantime, it is still a robust system with decent features and works reliably.
In comparison to X10 DS7000, SC-1000 is more expensive and the kit comes with less accessories. But if you want a good quality and reliable security system at an affordable price, the latter is a better choice.
Regarding the strobe light, it appears that Skylink currently does not offer such an accessory. It does offer a silent alarm socket (SW-433) for use with a light bulb for flashing visual warning.
The cheapest way is to buy from Amazon.com on-line. However, a reviewer suggests to purchase locally in case there is the need for replacement of defective components.
The SC-1000 basic kit is priced reasonably. But for future expansion of the system, the total cost of extra accessories may add up significantly. And I think Skylink makes more profit from the sales of accessories than the basic kit. If your priority is system cost, then X10 DS7000 may be an attractive buy.