"Any help would be great." This might be marginal for even "any help."
1. The XSi was a great camera when introduced. Newer bodies will take you to a different world, especially with higher ISO that might be needed in less than ideal light. More FPS will take you to a different world. I went from a 50D (6 fps) to a 7D Mark II (10 fps) and could not believe what I had been missing.
2. Will your games be at night under lights? If so, you will need a fast lens.
3. Since you want something longer than 200mm, be aware fast and long can be outrageously expensive. You might need to compromise somewhere.
4. I love my 70-300mm L for daytime soccer. It is okay for about half the field. I use my 70-200mm f/2.8 for night games and live with whatever I can get. A 100-400mm lens is often recommended for daytime soccer.
5. New body, three to consider:
7D An older model introduced fall of 2009, available new for $749.00
70D Introduced in 2013 It is a really good camera that will shoot 7 fps, available new for $949.00 Friends love theirs.
7D Mark II introduced fall of 2014 shoots 10 fps, available new for $1,349.99 It is a serious camera with many menu settings allowing the owner to tweak the performance or end up with a real mess. It has a serious learning curve to take advantage of all the features. High ISO quality is good and crop ability is amazing (at least compared to earlier prosumer cameras.)
Maximum budget of $3,000
7D Mark II for $1349.00 and Canon EF 70-200mm f/2.8L (non IS) for $1,349.00 for day and night games. Total = $ 2,698.00
or 7D Mark II plus Canon EF 100-400mm f/4.5-5.6L IS USM for $1,499.00 for day games. Total = $2,848.00
The 70D would save $400.00 I would not get a 7D.
Canon 7D Mark II w/Canon BG-E16 Battery Grip; Canon EOS 50D w/Canon Battery Grip; Canon SL1; Tokina 12mm - 24mm f/4 PRO DX II; Canon EF 24-105mm f/4L IS; Canon EF 70-200mm f/2.8L IS; Canon 70-300mm f/4-5.6L IS; Sigma 85mm f/1.4 EX DG HSM; Canon EF 300mm f/4L IS; Canon EF-S 18-135mm f/3.5-5.6 IS STM; Canon Extender EF 1.4x II; Canon Extender EF 2x II; Canon Speedlite 430EX II Flash
Image Editing Okay