Do you think that I should upgrade to an SSD?

Concur with roli59.
Although I have to admit that the 250/256, when on sale, are attractive. When I first bought my 120/128 gig sata III drives they where around $200, They have dropped off to $100 give or take 20 bucks.
On my 4 systems, windows takes about 35 gigs, Not a gamerer so if you want games you need to add games space. For the vast majority only 256 gigs is Not enough for everything, and you already have a HDD so you should keep it.

My choice of SSDs are the Curcial M4s and the Samsung 830's. The Vertex 4 looks attractive and probably the Agillity 4 (soon to be released), But NOT a lover of the company.

Rolli's choice of drive is a very good price, But I would not buy, would perfer paying more for a better drive. (ie their deluxe model has better performance, abiet still a SF controller). The stats: 1/2 egg reviews are kinda high at 19% vs 77% 4/5 eggs - Note must discount some of the 1/2 egg reviews as user probably installed wrong.

I tend to not look at benchmarks as manuf claims use ATTO benchmark and are inflated compared to real life - I prefer to use Reliability and LEAST user problems to detirmind Buy.