"Those are PassMark benchmark scores. PassMark is a benchmarking software which runs the CPU through many stress tests like
read/write operations, math calculations, and graphics processing. People who run PassMark can submit the score they got with
their processor so those charts are showing the average submitted scores for each processor. I wouldn't read into the overclocked processor charts much because they include mild overclocks as well as extreme overclocks, and there's no way to know how overclocked the processor was when it got the given score. If you really want to see specific scores, you can click a processor from the list and it will show the last 5 submitted scores along with information like RAM, measured speed, hard drive, graphics card, etc."
The Dell Inspiron 15R usually comes equipped with an intel HD 4000 graphics card. This is a mid level class 3 graphics card, which means it won't run CS Global offensive, but it will run CS source all right. Also, check if it's new and not refurbished at Costco because $599 is at least $200 below the market price of a new Inspiron 15R.
You shouldn't have a problem with your video, photo and music stuff, if you're using an i7 processor with at least 4-6GB RAM. No computer under $600 will support CS GO. You either have to spend more, or not play many games. Low end gaming laptops normally start from $800 above.
Don't focus too much on clock speeds. The average clock speed is around 2.3Ghz. Just because the clock speed is higher, doesn't necessarily mean the processor is better. 3rd gen processors normally have less power consumption and better performance. The core i7 processors are designed specifically to handle gaming, over and above the normal tasks, making them the best processors going, for now.
Here's the link for the Inspiron 15R. Starting price is $800.
It's got a 3rd gen i5 processor, which is pretty good. It's got 6GB RAM and a decent GTX 640M graphics card. I think you'll manage just fine with this. It's in your price range too. If you think you'll feel better with an i7, check this out...
Take a look at the links I sent you, before settling on the Inspiron. The Inspiron IS a good buy for you, but look at the laptop with the 640M card. It's a good card and will support CS GO if you want to play it. The A8 processor you've listed above is only an average processor. Both the i5 and the i7 that are in the comps I've listed are better. You don't want a HP. Their customer service sucks. If you run into problems, which is almost a guarantee 6 months down the line, you're going to have a really hard time. Anyway to answer your question, yes, you'd manage perfectly with the Inspiron.
Ok, don't worry about your music stuff. As long as you have enough RAM, you'll be able to run all the software you need. As far as audio hardware is concerned, you can easily connect external devices to enhance your audio experience. Keep in mind you're on a strict budget, so don't try to look for a laptop that has amazing sound and bass and stuff, on top of your original needs. You can work all that out after you've chosen a decent laptop.
Next, what do you mean by "its own RAM"? I didn't understand that. Also, don't get a refurbished laptop, just get a new laptop. Refurbished ones come with loads of problems. You need a GPU, whether you use an i7 or an i5. Even if it's an average GPU like the 15R's GPU, it will help with your gaming and video viewing. Get the Inpsiron 15R, because of the i7, GPU, RAM and Hard disk space. It's a good deal.