xml - Splitting tables in SQL Server 2008 -

we developing online advert site people buy , sell (similar gumtree) difference being used employees work company, wont reachable people outside company.

now have 15 categories have sub categories , sub categories have child categories.

we have main table called adverts consists on itemid, title, subtitle, description, createdby, broughtby, startdate, enddate , parentcategoryid, subcategoryid , childcategoryid etc

now instead of having 1 massive tables consists of details item selling going create separate table(s) per category details of item.

so have advert.vehicle_spec have details car selling i.e itemid (which fk main advert table), make, model, colour, mot, tax etc

that way when query main table advert can join onto relevant spec table in way keep tables clean , tidy question approach? there performance issues approach? create relevant fk needed queries etc.

i did ask question on sql server forum , 1 individual suggested using xml - each category gets xml schema , xml tags , values held in single field data varies depending on type of item being sold. requires more setup has best overall balance of performance , flexibility, have never worked xml within sql can't comment on being approach or not?

each category can have many different status's have variety of tables hold description of each status, queries performing vary select, delete, insert, update queries have multiple joins on status/user table, implementing "suggested" form show records suggested user depending on search for.

is xml right in regards flexibility , performance?

xml seems approach this, can directly write stored procedures queries specific categories want , organize them tables , display them. possibly want use xslt extract xml data , display them in table.