What would you be using this for? It's not a great mix of parts for either gaming or general use.
That Core i7 is 2 generations old, from before Sandy Bridge and Ivy Bridge. It's slower, uses more power and runs hotter. The video card is almost useless for gaming and is also 5xxx instead of 7xxx series.
For gaming, depending on budget you'd want an i3 or i5 CPU not i7. You'd want a better video card like a 6770.
For most general use, a Sandy Bridge dual-core Pentium and its built-in graphics are fine. That would use a _lot_ less power than the i7 + 5550.
Depending on prices in your area, 300 euros might not be a terrible price, but it's old used parts not new parts with a warranty. If it's being sold as new, then it's dusty old "new" parts from the back of the warehouse.