Hello,
Welcome to eUKhost forum
You have not mentioned the number of clients you host at the moment and how many new clients will be added up (if any) so I cannot really say whether a semi dedicated server is the right solution for you. Perhaps you may also consider a dedicated server to have complete control and flexibility to host more number of clients in future.
You can purchase a separate SSL certificate for each of your domain name hosted with us. We offer SSL Certificate from Certificate Authorities such as SBS and Rapid SSL. SBS certificates won't work with Google Checkout however RapidSSL certificate does. We can provide you SSL certificates from RapidSSL to use them with Google Checkout. Each certificate costs £25.00 per year which also includes a dedicated IP required for installation of the certificate.
You can install any third party applications on semi-dedicated server. Generally we don't install any modules with plain server however you can provide us the list of the applications you would like to install. If you opt for Plesk control panel then you will get following applications pre-installed :
Web Server: IIS
Scripting: ASP.NET 1.x, 2.x and 3.x, ASP, Perl, Python, SSI, SSL, CGI, Mod_Perl
More: MS FrontPage, Skeleton Directory
Mail : MailEnable
Web-based: IMP, MailEnable
AntiSpam: SpamAssassin
AntiVirus: DrWeb, Kaspersky
Mailing List: Mailman
DB's: MySQL 4.x and 5.x, MSSQL (Local or Remote), MSDE
DB Management: PhpMyAdmin, ASP.NET Enterprise Mgr
FTP Servers: MSFTP
Features: Anonymous FTP, Upload Directory, FTP Throttling
DNS Servers: Bind, MSDNS
Features: Master/Slave Management, Load Balancing, Automated File Matching
Stats Apps: AWStats, Smarter Stats, Urchin, Webalizer, Plesk Traffic Manager
Features: Real Time Bandwidth, Custom Reports, Graphical User Breakdowns
More : Integrated Sitebuilder Software, Backup and Migration Utilities, Configurable Firewall, International characters (UTF
, System Monitoring tools (Watchdog) and much more.
You have to purchase Plesk power pack for few modules.
Please feel free to post if you need any more information.